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Text and photos copyright © 2018 Steve D’Antonio Marine Consulting, Inc.

From the Masthead

It’s happened on countless occasions, most recently just a few weeks ago while on a sea trial out of a South Florida inlet.  The conditions were bumpy, 6 foot seas with a short period, (along with the most vivid case of sea smoke I’ve ever encountered in southern latitudes, the air temperature was in the low 40s, see photo).  Ideal as far as sea trials go.  The pilothouse was a busy place; the buyer, helmsman, mate, brokers, surveyors, mechanics etc. were all coming and going.  The helmsman was concentrating on safely piloting the vessel when it happened, an alarm began to sound, a moderately low level rhythmic beep, beep, beep.  Pilothouse alarms are common on large, complex vessels of this sort, and so initially no one was particularly concerned.   However, the longer it went on the more folks began to notice.  Predictably someone eventually said, “What’s that for”.  The response was silence, no one knew.   Eventually the source was identified, and it was not critical, however, how is one to know?

A few years ago, while making an early spring passage from the UK to Germany aboard a new vessel, through conditions that were positively horrendous, the windshield looked like the proverbial washing machine, a similar event occurred.  I was on watch alone, the other two crew members had gone off duty thirty minutes prior and were getting some much-needed rest.  As I sat in the helm seat hanging on to its arms, contemplating the next wave impact, an alarm sounded.  This time, however it was different, the vessel’s central monitoring system flashed a large red bar across the bottom of the screen which said, “FIRE”.  Indeed, this was a genuinely serious issue and there was no mistaking it.  As it turned out, a dashboard monitor had overheated and began to emit smoke behind the helm station, where, thankfully, a smoke detector had been installed.  As it turned out the problem was not serious, and shutting down the monitor resolved the problem for the moment.

I’ve been asked by boat owners and buyers on countless occasions, if there is a means by which disparate pilothouse instruments could be interfaced, strictly to create a central alarm panel.  It would simply consist of a panel with the names of various components, AUTOPILOT; STABILIZERS; DEPTH; ENGINE etc, each with its own pilot light.  When an alarm sounded, the light adjacent to the device name would illuminate.  It sounds like a simple concept, and yet to the best of my knowledge none exists.  While many components can be interfaced via an NMEA 2000 or N2K network, not every component has this option and even when it does, getting a simple alarm indication on a central display can be challenging.  It seems the best option involves the use of a vessel-wide monitoring system such as a Maretron or BÖNING, however, while I like these systems they are costly and complex and not easily added to an existing vessel, and they are probably overkill for the goal of obtaining nothing more than a central alarm system.

Thus, I’m throwing down the gauntlet, if a marine electronics manufacturer, or creative technician can come up with such a system, analogue or digital, and relatively easy to install, I suspect he or she would have no shortage of interested parties.

This month’s eMagazine feature article covers the subject of coaxial cable performance and selection.  I hope you find it both interesting and useful.

The Low Down on Coaxial Cables and Connectors

Coaxial cable is available in a range of sizes, types, and performance characteristics.  Cost is usually a good indicator of performance and quality. 

The axiom out of sight out of mind applies as much aboard boats as anywhere else and in my experience it is especially applicable to marine electrical and electronic systems.   Because flaws, faults and defects are not readily apparent in these systems, they tend to go unaddressed.  The issues are, however, often quite noticeable when one knows how and where to look.

Coaxial Cable 101

Take for instance the manner in which a radio transceiver ( a transceiver is simply a combined receiver and transmitter) or receiver such as a VHF, SSB, AIS, shortwave, GPS, cell phone, cellular or Wi-Fi booster is wired to its respective antenna.  With the exception of some Wi-Fi boosters, which use a data cable, in all of these cases the cable used for this application is known as coaxial, which is a reference to the inner and outer conductors sharing the same axis.  The inner core, it’s typically a series of coarse strands but may also be a single conductor, carries the signal while an outer tube-like grounded conductor, usually a braid or foil or combination of the two (the greater the coverage of the shield the better, it’s often expressed as a percent that’s typically between 65% and 95%), reduces loss or degradation of the signal while minimizing electromagnetic interference from other radio signals or electrical equipment.  Many homes in the US, Canada, Europe and elsewhere in the developed world have coaxial cable for television and in many cases internet applications, connecting external antennas, satellite dishes, cable TV, and internet service providers to television sets and routers in homes and offices.

The connection between an SSB tuner and the antenna relies on GTO cable, which is vastly different than coaxial cable.  It acts as part of the antenna, and the terminal on the tuner, shown here, should be insulated.

If an ordinary wire is used rather than a coaxial cable for the transmission of radio frequency, or “RF”, energy it will simply act like an antenna, transmitting signals inside the vessel (which often leads to interference with and malfunctioning of other equipment), losing those signals as they are received and sent to and from the radio and antenna.  The shield is grounded at the transceiver end and thereby keeps the signal contained within the cable and prevents the introduction of unwanted signals into the center core conductor.  The spacing between the shield and the center core is critical and must be kept constant.  Kinking, crushing or sharply bending (most coaxial manufacturers specify a minimum bend radius) a coaxial cable compromises this critical spacing, which will degrade the signal.  Removing the dielectric insulator, the material found between the shield and the center core and terminating or splicing the core and shield “manually”, like ordinary wires, also leads to signal loss and increases the likelihood of interference both to and from the cable.

Sharp bends stress coaxial cable and can affect performance, they should be avoided.

Additionally, any abrupt change to the dimensions or spacing of the core and shield causes a reflection of the radio waves back to the source, to the transmitter.  This phenomenon, known as standing wave, creates a bottle neck, through which signals have difficulty passing, ultimately degrading the transmission quality.  Standing wave is measured as a ratio, known as standing wave ratio or SWR.  In short, it’s a measure of the difference between the maximum RF and the minimum RF voltage along the cable.  What’s most important about this ratio is ensuring that it’s kept low.  If there are no reflecting sources, if the cable is uniform and properly terminated, then the SWR would, ideally, be 1:1.

Another  factor that affects SWR is the matching of the impedance or resistance of the cable, this is a function of the cable’s dimensions and construction, to the impedance of the devices to which it’s connected; the transceiver or receiver and the antenna.  When the two are matched, they appear “transparent” to the RF signal and reflections and thus SWR are minimized.  Most coaxial cables used for radio transmission and reception aboard have an impedance of 50 ohms, while some, such as those used for television, are 75 ohms.  It’s important that the correct impedance cable be used and that it match the antenna and transceiver/receiver in order to ensure a low SWR.

Cable Selection

A variety of coaxial cables are available, in a host of sizes, with a range of loss characteristics, and impedances as well as a range of quality and associated expense from many different manufacturers.  Selection can be truly confusing even for professionals.

Proper cable selection depends primarily on a few details.  Chief among these are the recommendations of the equipment manufacturer.  In many cases, the maker of a radio will very clearly spell out the type of cable that should, depending upon the installation conditions, be used.  In the absence of that information, however, additional criteria must be relied upon.  Begin with determining the frequency range of the equipment.  This isn’t as difficult as it sounds.  In general terms, the most commonly used radio equipment falls in to a few well-defined frequency ranges, the most common and those relying on conventional coaxial cable are HF, SSB or shortwave, which operates between 3 and 30 MHz (an abbreviation for mega Hertz, or million Hertz, named after German physicist Heinrich Hertz who made significant contributions in the study of electromagnetism, it’s a measure of the number oscillations that occur per second which defines the radio frequency, in the past it was often referred to by the designation it replaced, cycles).  Marine VHF radio (and AIS) frequency is between 156 MHz and 158 MHZ and cellular frequencies are between about 850 MHz and 1900 MHz GPS satellites, and receivers operate at about 1500 MHz  Wi-Fi tops the list at between 2.5 and 5 GHz or giga-Hertz, which is the abbreviation for a billion Hertz.

The reason the frequency is important where cable selection is concerned is the attendant inefficiency or loss; the higher the frequency the greater the potential for loss from the cable.  Thus, several protocols can be derived from this truism.  Gear that operates at higher frequency must use higher efficiency, lower loss cable (and connectors, more on those below) and the runs between the receiver/transceiver should be kept as short as possible, necessitating even lower loss cable.   Of course this is true of all radio equipment, low loss cable and short runs are always desirable, however, it becomes more critical for VHF, AIS and cellular/Wi-Fi gear.  Although the loss characteristics are not as great where SSB/HF/shortwave are concerned, these installations still can and regularly do suffer from poor cable selection and unnecessarily long runs or a combination of the two.

Heavy, extra low loss cable, like that shown here, is well-suited for longer runs and higher frequencies.  It’s bulky but worth the effort.

As in illustration of how coaxial cable loss may affect transmission characteristics I’ll share a scenario I frequently encounter aboard vessels I inspect.  A VHF radio is installed in the pilot house aboard a 52-footer.   The cable run from the radio to the antenna, which is mounted on an arch or mast above the fly bridge, is 40 feet, assuming the installer hasn’t left an additional 20 feet of cable coiled up beneath the helm, which is highly undesirable and not uncommon.  The cable “run” is a measure of actual linear feet rather than an imaginary straight line drawn between the antenna and transceiver.  The output of the VHF radio is 25 watts (or 1 watt on specified channels) and the cable that’s been chosen, for this example, is a common type referred to as RG 58U, is about 3/16 inch (4.7mm) in diameter, pretty gossamer.  The actual power output at the antenna-end of the cable is just 13.4 watts, or a reduction of 45%, the rest of the power has been “lost” in the cable run.  It’s important to remember, the type and location of the antenna has a considerable effect on the efficiency of the transmitted signal, however, in plain terms, the lower the cable’s loss, the better and the more power the antenna receives the greater its transmission (and reception) characteristics.

If, on the other hand, a more efficient cable is chosen, say RG-8X, a common, ¼ inch (6.3mm) diameter, higher efficiency lower loss cable, which is often used for VHF installations, with all other factors remaining the same, the wattage reaching the antenna increases to 16.9 or a reduction of 32%.  If a still lower loss cable is used, the Cadillac of coaxial cables and my personal preference, Times Microwave LMR 400, can be utilized, this cable is a hefty 13.32 inch (10mm) in diameter, the reduction in radio energy reaching the antenna is a scant 12%.  Now, imagine the same circumstances placed on a cellular coaxial and antenna installation. Recall that cell frequencies are many times higher (with loss many times greater) than those of VHF and their output power many times lower, and it’s easy to see how the performance can be significantly degraded.

Exposed coaxial terminals will corrode.  In wet locations, including bilges, they should be installed using a light film of dielectric grease, and then covered with heat shrink tubing or high quality electrical tape; if on weather decks these must be UV resistant.

As you can see, the price that is paid for low loss; essentially cable bulkiness (and commensurate expense) is very clear.  The same calculations can be carried out for other cables and transmission frequencies with some very startling results.  The high frequency of cell phones, for instance, coupled with their low output power of between a quarter and three watts (the latter for boosters) makes for very special coaxial cable requirements.  In this case low loss cable should always be used even for relatively short runs.  The same holds true for Wi-Fi applications and, once again, every effort should be made to keep these cable runs as short as possible.

Once a cable’s shield is exposed, and it has been exposed to the elements, it is almost certainly compromised.

By the same token, even though SSB frequencies are lower and thus less loss prone, the often long run between the transceiver and the antenna and/or tuner means these installations call for low loss cable.  Additionally, in spite of the fact that their output power is considerably higher, up to 150 watts, the range over which they transmit is significant, hundreds or thousands of miles and as such it’s worth the effort and expense of ensuring the antenna receives as many watts of transmission power as possible.  Thus, using RG8X for a 50-foot run between a helm-mounted transceiver and the lazarette mounted tuner would result in an 18% power loss, assuming other common loss or SWR matching inefficiency factors.  This may not seem like a significant number, however, once again, when the transmission distance is considered it may mean the difference between a voice communication that’s intelligibly received and one that’s simply ignored because it’s garbled, faint or static-laden.  If the Times Microwave LMR 400 cable is used the loss becomes just 7%.  Every watt counts when it comes to marine communications so don’t let an installer tell you it’s “fine” or “there’s no real difference”, insist on low loss cable.   Another note on SSBs, most utilize a separate antenna tuner that is or should be located close to the antenna, it’s connected to the transceiver using coaxial cable while the connection between the tuner and the antenna utilizes another specialized, non-shielded cable referred to as GTO-15.  Although it resembles GTO cable, coaxial cable should not be confused with or used in its place, GTO is actually a transmitting part of the antenna, and thus is thus it should not be run inside accommodation spaces.

When choosing coaxial cable, in addition to the criteria mentioned above, ensure that it’s suitable for marine applications.  Fortunately, this isn’t simply a way for manufacturers and retailers to charge more for a product that’s no different than other land-based versions.  Most marine-grade cable utilizes corrosion resistant tinned conductors.  The cable’s jacket may be white or black, although proprietary marine coaxial tends to be white.  The name of the manufacturer as well as the cable type, RG 8X or LMR 400 for instance should be clearly printed on the jacket.  Having said that, the lowest-loss cable may not be marine rated; in my opinion low loss trumps corrosion resistance.

While tinned, corrosion resistant conductors are desirable, some very low loss cable is not available in this format.  Given the choice, choose low loss over corrosion resistance.  Careful attention should be paid to waterproofing installations regardless of the type of cable that is used.


The other half of the coaxial cable equation involves the type and method of attachment of connectors.  Coaxial cables require special terminals that must be installed following clearly defined techniques, the transgression of which nearly always results in diminished performance, or worse, no performance at all.

A selection of coaxial terminals, each specifically designed for a particular cable type.

The volume of connectors available is nearly endless and quality of materials and construction covers a broad spectrum, from economy to gold plated, literally.  Connectors should be purchased from name-brand respected manufacturers (often, higher quality connectors are embossed with the manufacturer’s name) such as Amphenol, they invented modern coaxial connectors, Ancor, Shakespeare, Times Microwave and others.  High quality coaxial connectors are made of brass or beryllium copper with silver and/or tin plating and in some cases gold plating (the conductivity of silver is higher than gold and even higher than copper; however, gold does not tarnish, although silver’s silver oxide “tarnish” is conductive).  The insulating material between the center core and the outer shield should be capable of withstanding substantial heat for connectors that are designed to be soldered, at least 300°F.  Lower quality, and low cost, connectors often utilize a form of plastic whose melting temperature is well below this threshold, which makes a solid solder joint difficult to achieve without damaging this insulator material. Check these connector specifications before purchasing or specifying for others.

Failing to use solder on coaxial terminals that are designed to be soldered virtually guarantees poor performance.

Much like coaxial cable, connectors are available in many styles and varieties.  The key difference between them is the frequencies for which they are rated.  The most common connector, known as the UHF style, has been around for many years, having been invented by an Amphenol engineer in the 1930s.  Because its impedance is variable it’s only suitable for frequencies up to about 300 MHz, which includes HF/SSB/Shortwave and VHF.  The most popular designations for UHF connectors are PL-259, the male, and SO-239, the female portion that’s typically located on the equipment and in some cases the antenna.  Anything above 300 MHz, cell, GPS, Wi-Fi etc, requires a more sophisticated type of connector.  These lower loss units include N-Type, BNC, TNC and Mini varieties, all of which are typically available for most cable sizes.  The primary difference between the UHF and these other connectors is those suitable for frequencies above 300 MHz maintain constant impedance, which, at these frequencies, keeps SWR and RF transmission efficiency at an acceptable level.


At one time the only way to professionally install a coaxial connector for anything other than TV applications was by using solder.  It remains an excellent approach; however, many quality connector manufacturers now offer reliable solder-less coaxial connectors.  In some cases special crimping tools or dies are required while in other cases all that’s required is a needle nose plier.

Properly soldering coaxial terminals requires practice.  These “cold” solder joints are unacceptable, and all holes should be filled.

Proper solder joints, like the one shown here, are critically important.  These can be difficult to achieve if inadequate heat is available when, for instance, the termination is being made outdoors, in breezy conditions.

Whichever approach you use, be certain you understand how the termination is to be made.  A single hair-like strand of a cable’s shield that’s out of place can create a short, which in turn will cause the associated equipment to malfunction.  Most coaxial connector manufacturers include or offer detailed instructions for installation of their products, take the necessary time to familiarize yourself with the procedure, although not terribly difficult it’s often a specific multi-step process.

Great care must be taken when installing coaxial terminals.  A single errant shield strand, making contact with the center conductor, will cause a short and diminish performance. 

When coaxial cables are initially terminated they should be checked for both continuity as well as short circuits.  After installing connectors at each end and before connecting the cable to the antenna and transceiver or receiver, test for continuity between the shield and the core conductor using an ohm meter.

Testing cables using an ohm meter, after terminals are installed, can identify shorts and open circuits before the installation is complete.

The resistance should be infinite, i.e. no connection what so ever between the two.  Any connection, regardless of how high the resistance, is too much, it’s a short circuit that will degrade performance or prevent the gear from operating all together.  Then, using a jumper wire, connect the shield and the core at one end of the cable (make the connection between the center pin and outer body of the connector) and measure the resistance of the connection at the cable’s opposite end.  This will confirm that the connectors are properly installed and are making good, low resistance bonds with the cable.  In this case the reading should be exceptionally low, no more than one or two ohms, most of which is a result of resistance induced by the terminal to cable interface.  High quality coaxial cable alone, without connectors, possesses roughly 1.5 ohms of resistance per 1000 feet.

While it can be done manually, those preparing coaxial cable for terminal installation should utilize readily available special tools. 

Few coaxial connectors are designed to be water proof or even water resistant.  Therefore, installations on weather decks should take this into account and appropriate measures taken to prevent water entry into cables.  Because the shield used on most coaxial cables is made up of a very fine wire braid, it tends to absorb water via capillary action, even when it’s not directly exposed to free water, heavy fog or chronic high humidity will induce water entry into coaxial exposed shield.   Once that happens, the cable’s performance is almost immediately degraded.

A poorly made connection, it lacks water proofing.  Note the visible shield strands, these will act as wicks for water entry into the cable.

Coaxial terminations made on weather decks should be afforded the benefit of dielectric grease applied to the core pin and threaded or bayonet connection before assembly and then sheathing in heat shrink tubing or weather-proof electrical tape (before applying remove all traces of dielectric grease from the outside of the connector and, if using tape, be sure to start the tape wrap low and work upward to the attaching end of the connector, to create a water shedding shingle-effect in the overlapping wraps).  Additionally, if possible, include a drip loop so the cable does not act like a flume, channeling a stream of water toward the connection.

Ideally, this terminal should be completely enclosed in heat shrink tubing.

Because of the importance placed on the type of cable used and because the selection is dependent upon, among other things, the length of the cable run, antennas that are manufactured using en bloc female coaxial terminals rather than pigtail coaxial cables are preferred.  When the antenna manufacturer includes the cable as an integral part of the product the user is often stuck with a cable that may not be long enough, requiring a splice.  Additionally, if the cable is ever cut, crushed or damaged or if it becomes water logged, the entire antenna may have to be discarded.  Additionally, it’s possible that one may wish to utilize a higher quality cable than the one supplied by the antenna manufacturer, especially if a long run is involved.  Additionally, antennas that include a permanent pigtail preclude ohm meter testing of cable assemblies.  Some antenna manufacturers offer the same style of antennas equipped with either a pigtail or a female coaxial connector.  When given the choice, choose the latter so you can use the cable of your choice and so cable assemblies can be tested.

A heavy low loss cable transitions to a smaller diameter “pigtail” cable, one that’s permanently attached to the antenna.  While the bend in the smaller cable is too sharp, the heat shrink tube waterproofing is ideal.

Check This Out

Once all of the connections are made the equipment should be tested.  That means, for radios, radio checks from the greatest possible distance.  Any VHF radio check that’s from a vessel that’s less than 10 miles away is of limited value.  The call should not be placed to the Coast Guard, they have more important things to do and their transmitters and antennas are uber-powerful so it’s likely you’d make contact using little more than a wet mooring line as an antenna.  I once made contact with a Coast Guard communication facility in Portsmouth, VA while half way to Bermuda, roughly 250 miles off shore. Checking VHF operation by tuning in the weather channel also counts for naught when testing a coaxial and antenna installation.

For VHF installations, the only way to be certain the system is performing properly is to obtain a radio check form a distant station, one that is no less than 10 nm. away.

SSB radio checks should be performed both day and night, with successful nighttime radio checks occurring with stations more than 1000 miles distant.  Using an SWR meter on both VHF and SSB installations is an ideal way to check for satisfactory coaxial as well as counterpoise (for SSBs) installation.  Cell phone coaxial and antenna  checks are somewhat more challenging.  You can of course compare the number of available “bars” with and without the external antenna.  Clearly, if the external antenna affords you no additional bars, something is wrong.  Testing coaxial installations for AIS and GPS transceivers/receivers can be somewhat more challenging, however, at the very least the signal to noise ratio function should be accessed and their operation should be carefully scrutinized and compared to other receivers on nearby vessels when possible.  If something doesn’t appear right or if signals are inexplicably marginal or non-existent don’t ignore the problem, find it or seek professional assistance before relying on this gear.

This coaxial cable easily separated from its terminal, likely because it was not properly installed.  The boot shown here, while seemingly desirable, can actually retain water.  Heat shrink tubing or electrical tape is preferred.

Because the loss is difficult to quantify unless it’s actually measured, or the calculations performed, the user often has no idea of just how bad it is.  When I query boat builders or electronics installers about the cable (or antenna) that’s being used in a particular installation, its loss characteristics, length etc. the response is almost invariably, “it’s fine, that’s what we always use” or “no one has ever complained”.  In many cases, smaller diameter cable is chosen because it’s less challenging to run.  And, “fine” is relative, indeed, the VHF radio, GPS or AIS works with higher loss coaxial cable but how well?  After all, if you fail to make contact with your VHF or if an AIS signal from a vessel isn’t received, or if your AIS signal isn’t “seen”, or if you can’t get a GPS lock, will you know it or how often are you thinking that the culprit is the coaxial cable?  Now perhaps you will and you’ll know what to do about it.

Text and photos copyright © 2018 Steve D’Antonio Marine Consulting, Inc.

Photo Essay: Shore Power Plugs and Fire Prevention

Statistically, more boat and marina fires occur as a result of shore power than any other single cause, and more of those occur at the connections for shore power plugs and receptacles than any other location. In my experience, and frustratingly, nearly all of these are avoidable.

The potential energy available to a shore power connection, anywhere from 3,600 Watts to 12,000 Watts, is substantial to be sure; its ability to generate heat should not be underestimated. By comparison, a large space heater or hair dryer uses, or provides, a mere 1,500 Watts of heating energy.

Because shore power connections are made and broken routinely, the likelihood of developing a poor or high resistance connection is only exacerbated. In the world of electricity, resistance equals heat, in fact, the aforementioned space heaters and hair dryers rely on exactly this principle in order to operate.

In this month’s image, a 120 volt 30 amp (3,600 Watt) male plug is shown. Not only are its blades heavily oxidized (it looks as if this fell overboard once or twice), perhaps equally as concerning is the missing locking ring. When this plug is used with a connection that supports such a ring (a Y adapter for instance), the ring must be used, securing the plug in place. Unfortunately, nearly all dockside pedestals lack the ability to engage such a ring, making it especially important for users to ensure the cable is well-supported, with a wrap around the pedestal or by lashing it in place.

Inspect your cord connections regularly, clean contacts and use a corrosion inhibitor, secure cords, and replace missing locking rings and you’ll substantially reduce the possibility of overheating and fires.

Ask Steve

Hi Steve,

I saw your article on measuring exhaust pressure and thought I would share an experiment we did when I worked at Cabo Yachts. It all came about because we were asking our riser manufacturer to put a port in the riser as close as possible to turbo flange so we could measure back pressure. We kept coming up with back pressure numbers that were good on one boat and not great on the next. I noticed that the riser fabricators didn’t always get the port in the same place around the turbo flange and suspected that might be the problem. So we built the riser in the attached drawing. As you can see measured back pressures were all over the place. From that point on we always spec’d the port be perpendicular to the first bend of the riser (9 and 3 o’clock). Many engine manufacturers, if not all, now put their own ports in the engines which is where they want the pressure measured, but if you are depending on a riser manufacturer to place a port, then it really matters where it is on the riser.

Just thought you might be interested.  Have a good weekend.

Phil Arnold

Pacific Asian Enterprises/Nordhavn



Thank you for sharing this valuable information, things are rarely as simple as they seem.




Excellent article, as always.  It raises a question, though. Instead of a vacuum gauge on the filter manifold, why not do so as I have on a couple of my previous boats and put the gauge at the helm? No need for a drag needle, the operator monitors it real time. Using a flexible hose to connect the manifold to the helm-mounted gauge may not produce exactly accurate readings but all we need is relative readings indicating change in vacuum. Obviously a tight, secure installation is essential to prevent air leakage into the system.


Terry L. Johnson


Remote vacuum gauges make a great deal of sense, I’ve installed many for customers over the years.  It’s a luxury to be able to monitor vacuum real time from the helm.  Having said that, Racor mandates that remote gauges that are more than ten feet from the filter must be plumbed with metallic tubing or pipe (plastic can’t be used as it lacks fire resistance).   Hose runs over that distance can introduce inaccuracy into vacuum readings, and I’d argue that actual rather than relative readings are mandatory, 4 inches of mercury, for instance, is acceptable while 10 is not.  And, the longer the run, the greater the possibility of a leak.  Again, no issue with remote vacuum gauges provided they are installed and plumbed properly.  While it doesn’t provide real time monitoring, the drag needle gauge is simply easier to install and offers less risk of vacuum leaks.



Dear Steve,

I read with interest your article on zinc and aluminum sacrificial anodes online in Cruising World magazine.  My issue is that I do not seem to be able to find aluminum anodes for my twin Cat 3208 engines. One manufacturer told me that they do not make them for engines because they are too delicate for that use. My boat is kept in fresh water except for a few times at a week to a month in salt water, (Puget Sound). Is this an issue? The engines are fresh water cooled with heat exchangers.

Carlos Velategui


Conventional zinc anodes are of limited effectiveness in fresh water, when they are exposed to this environment they develop a coating that passivates them, thereby making them inactive.  Having said that, if you are unable to find pencil anodes for your heat exchanger I’m not sure I’d worry too much about it as a fresh water environment is far less corrosive to the metals found in a heat exchanger.  The primary issue is for those venturing into fresh water briefly, for a few days for instance, then back into seawater.  In that scenario, the mixture of seawater and inactive zincs, can present a greater corrosion risk.  Furthermore, aluminum anodes often develop a white frothy coating, which has no effect on their performance, however, when used in a confined application like a heat exchanger, it can make them difficult to remove when it comes time to replace them.  You can safely use aluminum anodes on your hull, and zinc anodes in your engine as they effectively reside in different bodies of water, and therefore will have no effect on each other.




I have previously attended one of your lectures and have certainly benefited from reading your articles and newsletters.  We have a 48 foot Kadey Krogen which we had built in 2011 and every year we spend about 6 months aboard in the winter time cruising the Bahamas.  The boat has really been a pleasure to own and we have had very few unexpected difficulties.    However we do have one area that is an annoyance and it is the use of aluminum with stainless steel fasteners in some of the components and walking many marinas it appears that it is a very common problem.    Perhaps in some of the components such as the Diamond Seaglaze doors, or the Steelhead davit stainless fasteners are necessary (perhaps) for strength in some locations.  In other areas such as aluminum vents etc. I don’t see that there should be any great need for an extra strong stainless screw.  I think that the airplane industry uses a lot of aluminum in their construction and would imagine that corrosion is an even a more dreaded thing in that situation.  I’m also of the belief that static electrical charge is an ongoing issue with airplanes. When you board an airplane and look at the door frames they certainly utilize bolts and screws in fastening them to the airframe which is also painted and they never show any corrosion or the typical bubbling of paint that we have to put up with on our boats and I believe that they also use the same kind of paint.

So I guess my question is if the airplane industry has solved this problem could the boating industry not have a look at what they do?  Perhaps there are airplane grade aluminum fasteners etc. that could be utilized in boat construction where aluminum is involved.    I can’t see where a couple of hundred specialized aluminum fasteners could be such a price that they would be extremely material in the pricing of boats.   I have gone through all of the areas on board our boat that I mentioned and removed all of the fasteners that I could and made sure that there was ample Teff Gel used when I refastened them.  That certainly seems to have helped but it doesn’t solve the problem.  Do you think that there is a type or grade of fastener that I might purchase to replace the stainless steel ones after repainting and touching up the paint so that it is not a continuous problem?

Thank you,

Perry Stickles


You’ve posed an excellent question on a subject about which I’m passionate, paint, aluminum and their interaction.  While there is some degree of galvanic incompatibility, and thereby galvanic corrosion, between stainless steel and aluminum (because aluminum resides in a very ignoble location on the galvanic series, it will interact with virtually any metal, not just stainless steel, when exposed to an electrolyte), the issue surrounding paint failure on aluminum is more a case of poultice corrosion (aluminum corrosion is described in this article    https://stevedmarineconsulting.com/wp-content/uploads/2014/03/Aluminum-Corrosion-Cruising-World-May-2017.pdf ).  That is, areas where fasteners, and their holes, penetrate paint, breaching its otherwise contiguous coating, allow water to migrate into, and become trapped between the paint and aluminum substrate.  Poultice corrosion sets in when the aluminum is exposed to this stagnant, oxygen depleted water, which in turn creates aluminum hydroxide, which in turn creates the unsightly paint blisters associated with this phenomenon.  The fact that the fastener is stainless steel plays only a small part, and I strongly suspect it would change very little if aluminum fasteners were used.  I also suspect this is less of an issue in the aviation industry because of the engineering that goes into fuselage design, all sharp edges are rounded (sharp edges promote paint failure), rivets are faired smooth and then they and the aluminum skin are painted, and all fasteners are installed using a sealing compound to help maintain cabin pressure and make the fuselage watertight.  Incidentally, I too look carefully at aircraft door frames as I board for the same reason, and I look for cracks, look up Aloha Airlines flight 243.  Additionally, aircraft are inspected for this issue regularly and repairs carried out as soon as paint failure becomes evident.

The real key to preventing paint failure on aluminum substrates is ample bedding.  Each time a fastener is screwed into, or hardware installed over,  a painted aluminum structure, it fractures the paint, even if only microscopically.  Each fracture becomes one of the aforementioned water ingress locations.  If, however, fasteners and hardware are thoroughly bedded in polyurethane sealant, the fractures are sealed, and the incidence of paint failure is diminished dramatically.  For more on this subject, see https://stevedmarineconsulting.com/paint-and-aluminum-how-to-ensure-a-good-mix-2/.

From the Masthead

Readers may have noticed that the Marine Systems Excellence eMagazine missed a deadline last week.  That was intentional, however, we also had every intention of alerting readers as to why this occurred, before it occurred.

The fall boat show season is upon us, which includes The International Boatbuilders Exhibition (IBEX), the Fort Lauderdale International Boat Show, and the Marine Equipment Trade Show (METS) held in Amsterdam, all of which I attend.  That, combined with an unusually heavy travel schedule,  has made it challenging for me to produce the detailed and high quality content the eMagazine requires.  Katie, our editor, along with her slew of other normal duties, has been equally busy with arranging my travel, as well as managing the upcoming Cruisers’ Workshop on October 21-22.  With all of that in mind, she and I decided that a fall ‘eMagazine Hiatus’ was in order.    The eMagazine will return in November.

In the meantime, the ‘From the Masthead’ column never sleeps…

Boat Building and ABYC Standards, Again

A couple of weeks ago I attended and lectured at IBEX, in Tampa, Florida.  It’s a place where those in the marine trades (along with a few die gearhead hard boat owners) come together to learn, teach and exhibit, and there’s nothing like it in North America, perhaps the world.  While METS is a stupendous show in its own right, and far larger, it lacks the educational component found at IBEX, and it’s that education aspect that makes it so incredibly valuable.  No true marine industry professional should miss this show.  Among other things, it’s an opportunity for trades people to pose questions in a non-judgmental atmosphere, with and among peers.  The discourse that results is unique and invaluable.  After one session a lecture attendee came up to me and asked the following question, “The boat builder I work for refuses to get onboard with ABYC Standards compliance, he thinks it’s a gimmick and will just drive up costs.  What can I do to change his mind?” .  I expressed my regret, saying he was not the first to share such frustration, and related the following story.

This is an actual case that occurred a couple of years ago.  It’s an all too common occurrence, a client expresses an interest in a vessel, whose specifications I then review.   After the initial review I prepare a set of questions for the builder, which include the following question “Is the vessel built to ABYC Standards and if so which ones?”  In this case, and most like it, the answer is a simple “yes”, which immediately raises concerns on my part because “yes” doesn’t really answer the question, and it implies the vessel meets every Standard, which is rare.  For those that do comply, meeting a series of the most important Standards, roughly 30 out of a possible 60+, is often daunting.  As I delve deeper into the review, which at some point, for a new build at least, includes a look at electrical schematics, it quickly becomes clear that the vessel’s design and systems are not ABYC compliant, at least not where the electrical system is concerned.  There are a series of violations, the most egregious of which involve the lack of fuses or circuit breakers, a potential fire hazard in the event of a short-circuit or overload, and the vessel’s shore power is not equipped with an ELCI, the equivalent of a whole-vessel GFCI receptacle, posing an electrocution hazard.  Other examples included a lack of means of reboarding, i.e. a ladder that can be easily deployed by a person who has fallen overboard, and LP tanks that are stored in a space under the flybridge helm console, along with a range of non-ignition protected electrical and electronic gear; representing an explosion hazard.  After pointing out these and a variety of other issues, the builder sheepishly responds by saying, essentially, he is an ABYC member, he knows they have a copy of the Standards, somewhere, and he thought they were compliant.

Let me be clear, where diesel-powered recreational vessels are concerned, ABYC Standards are purely voluntary, there’s no legal mandate to meet them, and this is often the retort  from boat builders when such violations are identified.  While strictly speaking that is true, any boat builder (foreign or domestic) that sells vessels in the United States, and does so knowing that they do not comply with at least the most important safety and reliability-related standards, electrical, fuel, LP gas, reboarding, exhaust system, to name a few, does so at their own peril.  When, for instance, I point out, as noted above, that a fuse is missing form a location where it’s required for ABYC compliance, and the builder balks, often saying, “We’ve been building boats for XX years and we’ve never installed a fuse there, and it’s never been a problem, why should we start now?” I usually respond by saying, in addition to the technical reasons for its inclusion, “Imagine yourself sitting on a witness stand, explaining to a jury why you didn’t install this fuse, which would have cost less than $50, after a vessel you built caught fire, and burned, injuring or killing some of those aboard. Because you are under oath you’d also have to say ‘yes’ when asked if you’ve heard of ABYC Standards, and if you were aware they called for the installation of this fuse, and that in spite of this readily available information you knowingly disregarded it, choosing instead to, and an attorney will emphasize this, save $50.  Do you want to find yourself in that position, and is it worth it?”

I’m not one to play the legal scare card, and I’d much rather boat builders and those in the marine repair industry follow these Standards because they make for safer and more reliable boats, but the litigious aspect cannot and should not be ignored.  If you are in the industry, think carefully about this and how you would deal with such a question, both legally and morally.  If you are a boat owner, or buyer, be sure to ask about compliance with ABYC Standards when considering a new vessel or when preparing to have work carried out on the one you own.



Text and photos by Steve D’Antonio

Photo Essay: (Not) Painting Aluminum

It’s a phenomenon I encounter on a near-weekly basis; virtually every vessel I’m aboard suffers, to one degree or another, from a failure  of painted aluminum surfaces.  This includes cranes, window frames, doors, hatches, arches and masts.

To a degree, aluminum, left to its own devices, is naturally corrosion resistant, (see this article for more on the subject); as soon as it’s exposed to oxygen it develops a tough, clear oxide film, negating the need for paint.  Unlike steel and iron, it is, therefore, not harmful to leave aluminum in its natural, unpainted state, and many commercial and military vessel operators take advantage of this attribute.

With some notable exceptions, such as the Dashew FPB series, most will agree that for pleasure vessel use, unpainted aluminum can be unattractive.  Make no mistake about it, with the exception of anti-fouling paint; the only reason to paint aluminum is to improve its cosmetic appearance.

Not only is paint an unnecessary addition to aluminum, applying it can be detrimental; it can actually promote corrosion (unless appearances dictate otherwise, this includes aluminum fuel tanks, I began specifying unpainted tanks more than  20 years ago).  Achieving reliable adhesion between aluminum and any coating is challenging.  The smallest breach in the coating nearly always leads to poultice corrosion, a phenomenon which can only occur when aluminum is both exposed to moisture and robbed of oxygen; an environment that often exists at the base of a nick or scratch on a painted surface.   This forms the toe-hold for poultice corrosion, which progresses to unsightly aluminum hydroxide-filled blisters and eventually coating failure.

The best defense against this scenario is to avoid painting aluminum weather deck hardware, along with cabins, decks and hulls (and tanks).  The next best option is to ensure coatings over aluminum remain intact; thoroughly bed all fasteners and hardware assemblies using polyurethane or polysulfide sealant, to seal paint which inevitably fractures in these locations during hardware installation, and make sure all surfaces that are to be painted are free of sharp ridges where paint is naturally thin, and all holes and edges should be radiused or beveled.

Ask Steve

Hi Steve,

I own Nordhavn 46/82.  Thank you so much for your article on Electric Shock drowning.  I have a few questions I hope you can answer.

  1. Our boat has an Olson isolation transformer. Is it needed to install an ELCI if the shore source of current is already isolated from the boat?  Wouldn’t an ELCI just be an unnecessary redundancy?
  2. I know that even if our boat has an ELCI or isolation transformer that it is still not safe to be in the water in a marina because of other un-isolated or unprotected vessels. The question I have is how far away from the marina is a safe distance to swim?  If the current is going back to its source then where is the source?  At the location of the fault, the boat, the dock pedestal?  If I am not in between the docks of a typical marina and am let’s say 100 feet outside the general perimeter of the dockage am I safe?
  3. Is it possible for the marina to provide this protection at their equipment rather than the boater?
  4. Finally, if I am not in a marina but instead at anchor running the genset is there any risk of electrocution?

Thank you so much for your time and efforts with our owners’ group.  Your expertise helps make my wife and me, with our 7 year old daughter, feel much safer.

Kal Blumberg


With one exception, ABYC Standards do call for the use of an ELCI in transformer installations, saying the following…


11.11.1 An Equipment Leakage Circuit Interrupter (ELCI) or Type A Residual Current Device (RCD) shall be installed with or in addition to the main shore power disconnect circuit breaker(s) or at the additional overcurrent protection as required by E- whichever is closer to the shore power connection.

EXCEPTION: Installations where an isolation transformer is installed within 10 feet (3 m) of the shore power inlet or the electrical attachment point of a permanently installed shore power cord and supported according to”

I would argue that an ELCI is more than just desirable in an isolation transformer installation, it’s necessary because the transformer’s case is not, and cannot be in order for it to provide isolation, grounded to both the vessel’s and shore side ground.  Typically, the case is connected to the vessel’s ground.  Therefore, in the unlikely event the case becomes energized with the shore side current, there is no path back to the source, and the breaker will not trip, and the case remains energized; in which case a person could complete the path by touching it and something that is referenced to the shore, such as a seacock, rudder stock etc.  An ELCI would present a defense against such a scenario.

The above-noted exception, by the way, is one with which I strongly disagree.  With very few exceptions, I believe shore power inlet wiring should be protected as close to the inlet as possible almost regardless of its length, as the up to 10 foot allowed unprotected run between the inlet and the transformer, or main panel if no transformer is used, is essentially only protected by the dock pedestal circuit breaker; these are notorious for being faulty.

How far away from energized docks one can swim is a difficult question to answer, among other things it’s a function of the salinity of the water and the current available to the fault, variables that are impossible to quantify at the time you intend to swim.  While there are no guarantees, generally speaking, the consensus among my marine electrical colleagues is to stay at least 150 feet from energized docks and ground stakes ashore.

The “source of power” is the transformer, which is typically located at the head of the dock or in the parking lot area.  It’s essentially wherever that transformer is grounded to earth.  Fault current will travel through the water, and to the land to which that transformer is grounded.

More and more marinas are installing ground fault protection at the point of power, the dock pedestals.  Unfortunately this has been problematic as the trip current ranges from 5 to 30 mA, and as such, for those in the lower threshold range, nuisance trips are very common.  The good news for you is, vessels equipped with transformers, isolation or polarization, are unlikely to suffer from nuisance tripping even at the lower range.

While I can’t guarantee it couldn’t happen, I am not aware of any ESD’s occurring with generator use (electrocutions on the other hand have occurred, it’s no different than shore power aboard, along with inverters).  If a fault occurs, the current will attempt to return to the genset, and it is unlikely this return path will be through the water, and even if it is, it’s likely to be direct, from a strut to a through hull, or through hull to a ground plate for instance, rather than spreading outward away from and around the vessel.  If you swam into that path it’s possible you could become a victim, however, again I am not familiar with any such cases.



Hi Steve,

I’ve been following your column and articles for many years for your valuable tips.

My question concerns bilge pumps, particularly for use in deep bilges where a separate float switch isn’t feasible to install. I’ve been using various pumps with built-in sensors which senses the depth of water, turns on, then supposed to shut off when the level drops…often it doesn’t, and runs and runs.

Another type of sensing pump run momentarily every 2 minutes, if no water is found it will wait for another 2 minute cycle.

On my pump the interval is every 12 seconds!

I seem to have to replace my bilge pump every year or so. Is this technology still evolving? Even float switch have become less dependable since mercury was banned.

By the way, I have a high-capacity bilge pump mounted below the floor boards with a separate float switch for when the day the deep bilge pump doesn’t answer the call.

There’s no oil or contaminates in the bilge to give false readings and no persistent leaks, a dry bilge.


Ron Bruno


Two solutions come to mind.  The first is Ultra Safety Systems Ultimate Pump Switch Mini.  It’s pretty small and will likely fit in the space you have.  Unlike the paddle type switches it’s a cylinder and thus has a smaller foot print.

Alternatively, you can use one of the pressure-actuated switches such as Jabsco’s Hydro Air.  The “sensor” or pressure bell can be located as much as 10 feet below the switch mechanism, making it suitable for deep, narrow bilges.

I’ve only resorted to the automatic pumps in very rare cases, I find them to be problematic as well.

Do you have a high water alarm?  If not I’d strongly recommend one.  While a stand-alone system is preferred, if you have no room for another switch, and if your bilge is typically dry you could attach an audible alarm to your bilge pump, which would sound an alert whenever the pump was triggered.



Hi Steve,

I have had a 1985 Ericson 38 in the Deltaville area for several years.  Recently, the dock master at Fishing Bay Yacht Club plugged in a Galvanalert cord to all the boats on our dock, and mine apparently popped a yellow “accelerated” corrosion indicator.

I have not had any unusual zinc activity, but sometimes if I run multiple AC appliances onboard the main outlet gets pretty warm.  Could that be related?

I am not clear about what to do next.

Do you have any suggestions?


John Cabell


The Marinco Galvanalert is a tool that measures DC voltage (DC voltage causes corrosion, AC, with rare exceptions, does not) on the shore cord’s green safety grounding wire.  While it can be somewhat useful, it can also be misleading.  Without a more thorough analysis, it’s difficult to determine the potential level of corrosion, as the Galvanalert’s literature provides no voltage thresholds or levels.

Having said this, if your vessel is not equipped with a galvanic isolator, it should be.  Doing so will almost certainly extinguish the “Medium Activity” indicator.  Galvanalert or not, every vessel that plugs into shore power should be equipped with a galvanic isolator, it’s cheap insurance against galvanic corrosion induced by other nearby vessels.

If your vessel is already equipped with a galvanic isolator, there’s a good chance it’s either not wired properly or it’s no longer operating; it should be tested and the problem corrected or unit replaced with one that meets the current ABYC A-28 standard.

The “warm outlet” should be investigated, removed, inspected and replaced of necessary.  If the outlet is sound it may be a wiring issue, don’t ignore this clue, it could be the precursor to a fire.



Hi Steve,

For producing a LOT of electricity, why wouldn’t a pto-powered hydraulic pump linked to a hydraulic motor directly attached to the alternator shaft work more reliably than any belt?


Bob Frenier


On the face of it that seems like a great approach, and it was used by some builders for a period of time, including Nordhavn.  I haven’t seen a new installation in years.  In fact it’s pretty darn inefficient, turning mechanical energy from the engine into hydraulic fluid pressure, which is then converted back into mechanical energy to turn an alternator, induces significant loss and inefficiency, on the order of 10% to 15%.  Additionally, it’s often difficult to turn an alternator fast enough using a hydraulic pump; that speed is needed not only to produce adequate energy, it’s also used to operate the alternator’s fan for cooling purposes.  In their heyday it was not unheard of for hydraulic alternators to overheat and even catch fire.

Text and photos by Steve D’Antonio

Copyright © 2017

From the Masthead

About a year ago a client of mine, I’ll call him Frank, had text exchange with a marine industry contractor, let’s call him Bill.  Frank asked Bill to carry out some routine work on his boat, work Bill has undertaken for Frank on other occasions in the not too distant past.  The price Bill quoted, however, was twice what it had been previously.  Granted, Frank now had a new boat, but the work was essentially the same, the same brand of equipment and a similar age.  Frank was a bit taken aback and asked Bill if he’d reconsider.  The way Frank phrased his request came out sounding as if he was bargaining or asking for a discount; he wasn’t.  Bill’s responses were short to begin with and they became even shorter at this point; after a couple of exchanges Bill essentially said, “Thanks, you’ll need to find someone else”.  Bill essentially fired Frank, an otherwise loyal customer.

Bill is good at what he does and is in demand, and I’m sure he thought, ‘I don’t need this’.  Still, with each text message I cringed, both parties were heading toward the inevitable unhappy ending, and I watched it, the proverbial slow motion train wreck.  Ultimately Frank hired someone else, who performed the work competently and effectively, so it’s unlikely he’ll ever call Bill again, and truth be told Bill probably doesn’t care.  But is this the best course of events for both parties?  No, absolutely not, it’s bad all around, Frank is unlikely to ever refer anyone to Bill and he’ll probably tell this story again and again.  Bill is busy now because the economy is on the rebound, but as all of us old marine industry hands know, that can and will change.  Good will is money in the bank, and it should be saved rather than squandered.

I’ve thought about this episode a great deal since it happened.  The sequence and outcome could have been avoided entirely, and here’s how.

  • When working with a marine industry contractor avoid using the word “discount”, it’s off-putting to marine industry professionals and rightfully so, why should they discount their efforts and hard-won experience? If the price is more than you can afford, or are willing to pay, you have a few options.  You can shop around for the same quality work at a lower price, or you can say, “That’s more than I’ve budgeted for this project, is there any way to do it less expensively?”  That leaves open the option for using different materials, or taking another less invasive, and perhaps less thorough, approach.  If the contractor is the only person who does what he or she does well, in the region, and he or she is busy, be prepared for a “No”.  There’s no harm in asking, provided it’s done professionally and respectfully.
  • If you are a marine industry professional, and you are good at what you do, and you are in demand, you must resist the temptation every day to become over-confident, cocky or worse, develop a reputation for being a prima donna.  That doesn’t mean you are obligated to negotiate or defend your fees if you don’t wish to, it simply means you say ‘no’ in a professional, polite manner, leaving the door open for the customer to agree to use your services on your terms.  When asked to discount your fee, if you don’t wish to, simply say, “I’m sorry the fee is not negotiable, but I’m convinced the value you’ll get for that fee is undeniable, it includes xx years of experience, x professional certifications and $xxx,xxx worth of tools and equipment to do the job properly, and I stand behind my work.  I’m certain you’ll be satisfied and I’m also happy to provide references”, delivered sincerely and without an attitude.  That response, which should take no more than 30 seconds to deliver, will make it clear the fee is the fee, and it does so without animosity or hard-feelings.
  • Finally, the Frank and Bill exchange should have quickly progressed to a phone call.  As I’ve said countless times in customer service and communication seminars and workshops, it is very difficult to convey intent, sentiment and tone in an e mail or worse, a text.  In Frank’s case, after he received the quote, which was double the previous fee, he should have called Bill and said, “Bill, maybe I misunderstood, but the fee is much higher than the last time you did this work for me, what’s changed?”  The likelihood of a dispute being settled amicably is far greater when it occurs  in a live conversation rather than electronically.

This month’s eMagazine feature article covers the all too important subject of electrocution prevention.  I hope you find it both interesting and useful.

Electric Shock Drowning and ELCIs Explained

An equipment leakage circuit interrupter or ELCI, is capable of sensing faults in a vessel’s AC electrical system, whereupon it will turn off power in the blink of an eye, ideally before an injury or fire can occur.  With few exceptions, ABYC and CE-compliant vessels must be equipped with this component.

In 2012 three cases of electrocution or electric shock drowning (more on that below) occurred over the Independence Day holiday.  Tragically, they resulted in the deaths of four children, siblings Brayden and Alexandra Anderson 8 and 13 respectively, Noah Winstead, 10, and Nathan Lynam 11, and one adult, 26-year-old Jennifer Lankford.  All of the events occurred on lakes, one in Tennessee and the two in Missouri.  More recently, on April 20, 2017 three more cases occurred, in which 15-year old Carmen Johnson, 34-year-old Shelly Darling and 41-year-old Elizabeth Whipple were all killed while swimming in Alabama’s Lake Tuscaloosa.  In June of this year five more people were killed at a water park in Turkey, again by electrocution or electric shock drowning.

The most reliable way of preventing electric shock drowning is to avoid swimming around docks with shore power.

Each year electrocution, in most cases more accurately referred to as electric shock drowning or ESD, more on that in a moment, events such as these occur and each year a hue and cry goes out within the marine industry to educate boat owners, marina managers, marine electricians and swimmers about the dangers associated with swimming around boats that are plugged into shore power, or other shore power devices such as electric boat lifts.  Sadly, for these people, most of whom are children, and their families, it’s too late; however, it’s not too late for you to learn about these potentially disastrous scenarios and how to avoid them.


You would be hard pressed to find an adult who is unfamiliar with the ubiquitous Ground Fault Interrupter or GFI receptacle.  Found in household kitchens, bathrooms, patios and garages among other locations, and recommend by the American Boat and Yacht Council for use in heads, galleys, engineering spaces and on the weather decks of boats, they have no doubt saved countless lives since their introduction in the late 1960s.  Requirements for GFI’s have been part of the National Electric Code for over 50 years, with the first mandate being inspired by electrocutions caused by underwater lighting used in swimming pools.

In a properly functioning marine electrical system, the same amount of AC current flows in the hot and neutral wires.

However, if electricity “leaks” from this intended path in these two wires to ground, this condition is called a ground fault. A good example of this is an insulation failure in the wiring of an appliance.

In addition, a faulty ground can occur when the grounding path is broken through a loose connection or broken wire. For instance, a shore power cord ground wire may fail due to constant motion and stress.

Wiring diagrams and associated captions courtesy Blue Sea Systems.

While GFI’s have been covered in a previous column, there is yet another shore power safety device, one that was only introduced to the marine market within the last decade, that’s also worthy of attention.  Referred to as an Equipment Leakage Circuit Interrupter or ELCI (sometimes referred to as RCD’s or Residual Current Devices), it offers yet another level of protection from shore power faults, fire and electrocution or ESD.  Much like a common GFI receptacle (these have a comparatively low trip threshold of 5 milliamps, and as such are considered to be appropriate for protecting people, they represent local protection), ELCI’s remain in a state of equilibrium, allowing energy to flow, as long as the current on the hot and neutral wires, the two current carrying conductors found in most AC electrical circuits, remains the same.  As soon as current finds an alternative path back to its source (contrary to popular belief, electricity does not seek ground, it seeks to return to its origin, in this example likely the transformer at the head of the dock), through a green safety ground wire, the water or a human, the imbalance trips the ELCI’s circuit breaker and the power is turned off nearly instantly, often within 30-70 milliseconds.

Like GFI’s, ELCI’s (sometimes referred to as RCDs) must include a test feature, the blue button with embossed T.

While technically deemed “equipment protection”, because of their 30 milliamps trip threshold, the goal of ELCI’s is to interrupt current flow quickly enough to prevent electrocution, electric shock drowning or fire, and for the most part they do so very effectively, saving, much like GFIs, countless lives every year.

The adoption of the ABYC ELCI Standard was, much like the GFI, inspired by a number of electric shock drownings or ESD’s.  Different than a conventional electrocution, an ESD can, with comparatively little current flow, paralyze a swimmer’s voluntary muscle reflexes, causing him or her to drown, which only serves to mask the underlying electrically-related cause of death.  For more on ESD and how it occurs and differes from conventional electrocution, see this Marine Systems Excellence article.

“Electrocution” is a broad term, and the range of current has many differing effects.  Those that may be non-life threatening ashore, such as muscles freezing, can lead to drowning while swimming.

While it’s true that virtually all documented ESD cases have occurred in fresh water, the risk of swimming around docks and boats that are energized with shore power, in salt or fresh water, remains extremely high.  Some will say, “It can’t happen in salt water”, and I cringe each and every time I hear this.  There are several reasons this “theory” represents dangerous folly.  One, it’s impossible to determine the salinity level of a body of water before jumping in to cool off.  In estuarial waters like the ones where I live, on the Chesapeake Bay, salinity changes seasonally and even daily after heavy rains.  Two, it’s impossible to rule out the potential for ESD or electrocution in seawater provided the current flow is high enough.  Do you want to risk your life or the lives of your loved ones by testing this belief?  Some have also said that if an ELCI, leakage warning system or transformer is used, it’s then safe to swim in the vicinity of energized docks and boats.  Again, this is incorrect; it’s dangerous and risky at best.

Ground fault interrupter receptacles have been around since the 60’s.  Having saved countless lives in that time, they should be installed in a vessel’s head, galley, on weather decks and in engine rooms and machinery spaces.  They provide local protection and are still required even for vessels equipped with an ELCI.

In addition to the trip threshold, the primary difference between the ELCI and its cousin the GFI, is the location in which it is installed.  GFI receptacles are installed where power is to be used, galley, head etc, while ELCI’s are installed where power enters the vessel, near the shore power receptacle.  Think of it as a whole boat GFI with some modifications.  A primary shore power circuit breaker is already required for every shore power inlet, and in the case of an ELCI it is often installed either in conjunction with this breaker, or as a single combined unit, achieving the goals of over current protection and fault protection.  It’s important to note that the presence of an ELCI does not negate the need for individual GFIs, both are still required for ABYC compliance.

ELCI’s, the blue-handles, are often combined or co-located with primary shore power inlet circuit breakers, the black two pole devices to the right of the ELCI.   Don’t assume an ELCI trip current is correct, as they are available in a wide range, from 5 mA through 100 mA.  ABYC compliant ELCI’s should be designed to trip at 30 mA, those seen here indicate this in the “I=0,03A” shown on their face. 

ELCI’s got off to a rocky start when they were first introduced to the ABYC Standards and the marine industry in 2008.  As is often the case, the intent preceded the hardware, and as a  result the implementation was postponed for a couple of years.  Now, however, proprietary marine ELCI circuit breakers are readily available from several manufacturers in a range of configurations. With few exceptions, new vessels that are built, or those that are being refit, to ABYC (or European CE) Standards must be equipped with ELCIs, and with good reason; they save lives.  An ELCI can be added to virtually any vessel’s shore power system provided it is free of faults.

If the wire-run distance between the shore inlet and the circuit breaker panel is less than 10 feet, the ELCI may be located in the latter.

Folks often ask me when it’s OK to swim around docks, saying, ‘What if the vessel does have an ELCI?” or “The dock has a leakage warning system, is it OK then?”, or, “Can the water be tested before swimming?”. Unfortunately, the answer is no to all of these scenarios for a variety of reasons, including and especially because faults occur in a split second, one minute the water is safe, the next it’s deadly, and unless you can walk on water you can’t count on being able to get out of harm’s way quickly enough.   Also, as wonderful as ELCI’s and GFCI’s are, they are not foolproof.

You might ask, “What about divers?  I see them in the water in marinas all the time and they don’t get electrocuted”.  Whenever I encounter one on a dock, and that’s often, I make it a point of asking, “Do you ever get shocked or feel a tingle?”  Without exception every one has said yes, several have told me they can feel electricity coursing through their dental fillings.  A dry, and even wet, suit does offer some protection against electrocution and ESD, which is why these folks probably haven’t become victims.   They do this work at their own risk, hopefully knowing the hazards (one was killed recently in Florida, albeit by a bow thruster rather than ESD), a far different scenario from your child frolicking in the water on a seemingly care-free summer day.

Simply put, never swim around docks equipped with shore power in fresh or salt water. There are no exceptions to this rule.

Next month I’ll discuss shore power transformers and the role they play in electrocution prevention, and fault avoidance.



Text and photos by Steve D’Antonio

Copyright © 2017

My Love/Hate Relationship with Bilge Pump Control Panels

While it’s often given short shrift, bilge pump design and installation is every bit as important as propulsion or steering.  The system must work properly and efficiently, all the time.  A single failure can lead to costly damage or the loss of a vessel.

For this reason, I carefully scrutinize these systems aboard every vessel I inspect and sea trial.  In addition to the pumps and their installations, control and annunciator panels play a critical and often overlooked role in bilge pump applications.

Among other things, every bilge pump installation should include a visual indicator of pump operation, i.e. whenever the pump is running a light is illuminates.  Times have changed, the bilges of a modern vessel are for the most part dry, so it makes sense to include an audible annunciator for any bilge pump operation, rather than just high water.  If a pump runs, a not unpleasant chirp or buzzer should sound, while flooding would sound a louder and impossible to mistake alarm.   Additionally, the manual position in the familiar AUTO OFF MAN switch should not be spring-loaded or momentary-on, you should be able to turn it on and leave it on.  If the float switch fails during a flooding episode, it shouldn’t be necessary to have someone man the switch to keep the pump running.  On a similar note, it should be difficult to inadvertently turn a bilge pump switch off, ideally switches should be protected or covered.

The switches in the accompanying image are spring-loaded in the manual position, and they are exposed, making it more likely that they could be inadvertently turned off, particularly where they are located, adjacent to the engine key switch and trim tabs.  On a positive note they are equipped with indicator lights, however, in the bright sunlight of a flybridge, which is where these are located, it’s unlikely they’d be noticed, making an audible annunciator all the more valuable.

Ask Steve – August

Hi Steve,

I just read your helpful article on galvanic isolators in PassageMaker Magazine.

Would a good inverter do the same as a galvanic isolator?

If using a galvanic isolator, can both 50 amp shore power cords run through one isolator or do you need two?

If not, could an inverter on one power cord and an isolator on the other one work?


Dave Mckusick


You’ve posed a good question.  Unfortunately, inverters, when in bypass mode, where shore power is passing through them, do not, and cannot, isolate shore and vessel ground, and therefore would not provide isolation from galvanic current.

You can obtain galvanic isolators rated for 100 amps, through which both 50 amp shore power cord safety ground wires may be routed.  Therefore, yes, you can use one isolator for two 50 amp services, however, do check pricing as a single 100 amp galvanic isolator may cost more than two 50 amp units.  Whichever unit you choose make certain it meets the latest (2008) ABYC revision for this standard.


Hi Steve,

We have a question about running our diesels. We have an Azimut 46 with twin Cat 3208’s 435 hp. WOT is around 2800 rpm. We do about 28-29 mph. We usually cruise around at about 1000 – 1200 rpm unless we want to get somewhere then we run up around 2000 rpm. Fuel economy for the last 57 hours was about 4 GPH which is great.

Our question is: Is there any problem running the engines at lower RPM’s vs. the 1800 – 2000 rpm. Does it put more wear on the engine at lower rpm’s? Engines are in great shape with only 490 hours and doesn’t burn any oil.


Dan Woodworth


If I had the proverbial nickel for every time someone asked me this question.  Seriously, it’s a good question and I’m glad boat owners are more and more conscious of chronic under loading and the issues it can cause.  I’ve written a few columns on this subject, and this give me a good opportunity to reiterate my thoughts.

I recently read a boat review in which the reviewer boast that, because the subject vessel achieved cruising speed while using only a fraction of the engine’s available power, the engine should therefore last “forever”.  It’s a concept that’s commonly misunderstood, and one that seems counter-intuitive, the lighter the load on your engine the greater the likelihood of developing problems.  It’s true, when a diesel engine is chronically under-loaded several phenomena occur that conspire to shorten the life of the engine and increase the need for maintenance and possible repairs.

The environment inside a diesel engine combustion chamber is a hellish one indeed.  The temperature can reach over 1000°F while the pressure may be many times that of the atmosphere outside the engine.  Interestingly, however, this is how a diesel engine is designed to operate, at comparatively high temperature under relatively high load.  The high pressure found within the combustion chamber represents the very philosophy of the diesel ignition process, compressing the air increases its temperature, which in turn enables it to ignite the subsequently injected fuel.  Ideally, a diesel engine should be loaded beyond 50%.  When operated in this manner the temperature within the engine ensures efficiency and longevity.   Contrary to popular belief, while they may have improved defenses against it, new, electronically controlled engines are not immune from issues created by chronic under-loading.

When discussing proper operating temperature it’s important to remember that there are several regions within the engine, all of which may be operating at different temperatures under differing load conditions.  For instance, when you start your engine and run it at idle or at low rpm you may notice that the temperature gauge, it’s measuring coolant temperature, doesn’t move very much.  If it’s graduated in numbers as it should be it’s unlikely that the needle passes 140°F.  When a load is applied, on the other hand, if you are motoring hard to make port before a weather systems descends upon you, then the needle should hover around the engine’s maximum design operating temperature, which for closed cooling system engines is typically between 160°F and 195°F.  In the light load condition, when the coolant temperature is low, it means the temperature of the combustion chamber is also lower than that which is optimal and this leads to the formation of excess soot or carbon, which is deposited on the piston rings, injectors and valves, a scenario which reduces efficiency and may shorten the life of these components.   Cylinder wall glazing which exacerbates blow by, also occurs when an engine is chronically under loaded, especially early on in its life.  Because they are often chronically under loaded in the critical break in period, the first 50-100 hours, generators are notorious for suffering from this malady.  Even under moderate load, when the coolant reaches a normal operating temperature, unless the engine is equipped with an oil cooler thermostat, the oil temperature often remains cooler, too cool for optimum operation.  This is a significant and often overlooked aspect of under-loading.  Few engines are equipped with an oil temperature gauge; however, you can measures yours my “shooting” the approximate vertical and horizontal center of the oil pan with an infrared pyrometer.

The consequences of running an engine with “cold” oil are an increase in sludge and varnish production within the oil as well as an inability for the oil to vaporize water that accumulates as a result of piston ring blow by, which itself is exacerbated by the aforementioned carbon formation.  Blow by is essentially combustion chamber gasses “leaking” past the rings into the crankcase, a small amount of which is normal, carrying with them some water that’s part of all diesel exhaust.  Whether the blow by is normal or excessive, the water can only evaporate when the oil gets hot, over about 160°F.  Sludge is a combination of water, carbon and other contaminants, it impedes oil flow and, as the name implies, it’s greasy and often brown or tan in appearance, while varnish is a precipitate that is much harder, like, well, varnish, it adheres tenaciously to metal surfaces within the engine.  Both of these contaminants are harmful to an engine as they starve vital components of lubricating oil.  The bottom line is, avoid chronically under loading your engine and, if you must do so, run it up to 75% load for 10-15 minutes out of every four hours to stem the sludge, varnish and carbon tide and perform oil analysis with each oil change.  The former will increase oil and combustion chamber temperature to preferable levels, thereby reducing build-ups, and the latter will alert you to contaminant related issues caused by under-loading before they become critical.



I have a question that I hope you haven’t answered already.

I am anticipating having some work done on my boat this winter, located on the hard in the Philly area. Covered but no shed.

This will include removing center fuel tanks, and installing a house battery bank in that area. This work will also include rewiring the 3 way switch and adding an isolator.

I’ll also be adding a Glendinning synchronizer for Ford Lehman 135 engines.

I don’t know what if any impact this might have on the hull or parts involved and wanted your input on any issues that could arise with respect to the fiberglass or parts and if so what I should look out for or whether you think work should be held-off and done in the spring?

As always, thanks for what you do and the help you provide to boaters everywhere.

Best regards,

Charles Williamson


Adding a battery bank, one that’s replacing a fuel tank, along with the other electrical and engine tasks, can encompass a wide range of options, making it somewhat difficult for me to anticipate the variables.  Having said that, those carrying out the work should agree to do so while meeting guidelines set forth in ABYC E-10 Storage Batteries; E-11 AC and DC Electrical Systems; H-33 Diesel Fuel Systems and P-4 Marine Inboard Engines and Transmissions.  Needless to say, those carrying out the work should belong to ABYC and, ideally, hold an electrical certification.

Carrying out these tasks during the winter shouldn’t play a significant role unless fiberglass work will be done, in which case the vessel will needed to be both heated and ventilated.



I have a 2007 SeaRay 40 MY that I cruise along the St. Lawrence River and up the Rideau Canal and Trent-Severn Waterways.

After a recent holiday in Montreal we departed the Old Port only to find our engines overheating badly.  It turned out that I had left the 2 seacocks closed which supply cooling water to the engines.  Opening the seacocks failed to solve the problem because the impellers had been completely destroyed.  After a rescue by the Coast Guard, we were able to replace the impellers (with our spares) and resume our travels.  We noticed, however, that there continues to be a burning rubber smell in our aft bedroom while we’re underway.

Is it possible that the exhaust hoses have some rubber parts that have now been fried on the inside?  And might these pose a risk of fire in the long term?

Thanks for all the great advice you provide.  It’s comforting to know that there are independent experts to turn to when things go wrong.

Dr. Mike O’Connor


A failure like this is a heartache and all too common, boat owners make this understandable error very often.

Depending on how long you ran, and under what load, you almost certainly did some damage to the otherwise wet exhaust system, which is made up of fiberglass and rubber components.  These aren’t designed to operate at much over 200° F, while dry exhaust can approach 1000° F; it doesn’t take long for it to do significant damage to these parts.

I don’t believe there’s a risk of fire, however, there is a risk of flooding and fume ingress, if these “soft” parts have been overheated, they could leak both water and exhaust gasses into the cabin.  The entire run, end to end, should be inspected for heat damage.

While it is little consolation to you now, the entire episode could have been avoided if the exhaust system had been equipped with a temperature alarm, these are readily available, inexpensive and mandated for ABYC compliance.  I wrote about them in this article https://stevedmarineconsulting.com/onboard-alarms-part-i/.  I strongly recommend you fit a set to avoid a re-occurrence.

Text and photos by Steve D’Antonio

Copyright © 2017

From the Masthead

Apprenticeships Revisited

Readers of this column know that I’m passionate about marine industry professionalism and expertise, an integral part of which involves vocational training and apprenticeship programs.  I’ve written about these programs in other countries, notably Australia, and have lamented the dearth of such options within the American marine industry (as well as other technical trades).  According to the labor department, nine out of 10 Americans who complete apprentice training find a job with a starting salary of $60,000 a year.  An article in a recent issue of ‘Soundings Trade Only’, a marine industry journal, details the latest efforts by the Trump Administration to expand and enhance vocational and apprenticeship opportunities in this country.  I welcome and applaud this effort, which sends a clear message, not only is college not for everyone, there is a clear need, and respect, for those with a technical rather than academic education, and the need for skilled, well-trained and experienced professionals within this industry has never been greater.  Boat builders, dealerships and boat yards have been clamoring for skilled staff since the recession ended, and they report the employment gap grows with each passing month.  When I managed a Virginia-based boat yard, my greatest challenge involved the pursuit of skilled professionals; ultimately forcing us to recruit nationwide.  That was ten or more years ago.  With each passing year propulsion and onboard mechanical and electrical systems become increasingly complex, driving up demand for those who have the skills to install, maintain, troubleshoot and repair them.  I will continue to watch, write about, promote and report on this trend.

Nikita cruises before a waterfall, in what is acknowledged as one of Norway’s most picturesque regions, Geirangerfjord. 

Cruising Technology

I recently completed an 18-day passage aboard a Fleming 75 in Norway.  The vessel proved as interesting to me as the breathtaking Scandinavian scenery.  A 2004 model, Nikita recently underwent a lengthy refit, during which, among other things, she received a new navigation and communication suite, a Maretron monitoring system, and lithium ion battery bank.  The latter was of particular interest to me.  Thanks to, among other attributes, their light weight, dense capacity footprint, and rapid recharge time, lithium ion batteries, now common place in automobiles, hold great promise for marine cruising vessel house battery banks.  In the last couple of years, and thanks to early adopters, they have progressed from bleeding to cutting edge technology.  Spending time aboard this vessel allowed me to carefully evaluate both the installation and performance of this system.  While there remain a series of caveats for their use, I’m pleased to report that the results from this vessel were very encouraging.   I’ll cover the details in an upcoming article.

This month’s eMagazine feature article covers the subject of advanced battery charging and alternator regulators.  I hope you find it both interesting and useful.

Alternator Regulation

Without properly designed and installed advanced regulation, high output alternators will be unable to effectively, safely and rapidly charge large house battery banks.

A few years ago I inspected a new, and finely-crafted 57 foot single screw cruising vessel, whose 12 volt (by all rights the vessel should have been 24 volt, but that’s another story) house battery bank possessed over 1000 amp hours of capacity (an amp hour is the typical unit of measure for deep cycle batteries and large battery banks, one amp hour represents the usage of one ampere for one hour, while ten amperes of usage for four hours equals forty amp hours and so on).  Just a few years ago this would have been considered a huge battery bank, however, by today’s onboard electrical standards it’s moderately-sized for a serious cruising vessel.

The owners’ complaint was a refrain I’ve been hearing for most of my nearly three decade-long professional career; “The battery bank isn’t big enough”.  Although I suspected I knew why this cruising couple was saying this, I inquired as to why they believed this to be so.  The response, “the batteries aren’t lasting long enough between charging cycles, in the morning the batteries are nearly dead”, confirmed my suspicion.  Indeed, the battery bank required all too frequent re-charging, but not because it was undersized (if anything it was over-sized when compared to the charge capacity).  The problems lie in the method(s) of charging.

The vessel was equipped with a stock alternator supplied by the engine manufacturer, with a 100 amp capacity.  While this may seem like a lot at face value, it’s woefully undersized for the task.  Furthermore, because the alternator was internally regulated, as nearly every stock unit is, it was incapable of recharging a large house battery bank with any degree of efficiency.

Alternators, Not all are Created Equal

It’s important to note that most marine engines are industrial blocks that are marinized; they are destined for trucks and other industrial applications where the primary requirement of their alternator is to recharge a starting battery whose amp-hour capacity is often something less than 100 amp hours.  Most marine engine manufacturers follow a similar regimen, the alternator is designed to charge the engine’s own starting battery, as well as supplying power for pre and post heat systems (this is why more and more diesel engines are equipped with seemingly large alternators, as the heating elements are exceptionally power hungry, albeit for a short duration), instrumentation, electronic engine control if so equipped etc.  The average engine start cycle requires less than one amp hour, thus replacing it requires very little effort or time on the part of a stock alternator.

Insidiously, some stock alternators are deceiving in that their output is seemingly high, as in the case of the aforementioned cruiser, offering a hundred or a hundred and fifty amps.  The problem with these alternators is two-fold.  First, they are internally regulated and therefore not equipped to deliver the multi-stage charge required by deep cycle house batteries.  Second, with few exceptions they are not designed to deliver their full output except for short periods of time.  When called upon to do so, by retrofitting one of these alternators with an external regulator as is sometimes done, they often expire prematurely as a result of overheating.

Because they are unable to dissipate heat, most stock alternators supplied with engines are not designed to be externally regulated, regardless of output rating.  A healthy stock alternator’s lacquered copper windings (above) remain bright and shiny, while the windings of an over-heated stock alternator (top), one that was externally regulated, show clear signs of heat stress, wherein the lacquer coating has been vaporized.

The difference between a near-continuous duty high output alternator and a high output stock alternator is, to paraphrase Mark Twain, like the difference between lightning and a lightning bug.  The trouble, however, doesn’t end here.  Not only is the stock alternator not equal to the task it’s being called upon to carry out, even when externally regulated, its output, contrary to initial perceptions, is simply inadequate.  While 100 amps may appear substantial, it’s anything but when compared to the massive bulk of many of today’s house battery banks.  In the case of the 57-foot cruiser, it’s a mere 10% and even if it was a proprietary, continuous duty high output alternator it still would be inadequate.

A handful of stock, off the shelf high output alternators are capable of being externally regulated.  This Leece Neville/Prestolite model is one example, it produces 175 amps at 24 volts.

Depending upon the battery type, flooded, gel or AGM, the rule of thumb for the ratio of charge output to battery bank size calls for the charge source, an alternator(s) in this case, to be a minimum of 25% of the bank’s amp hour capacity (gel batteries can initially accept 50% of their amp-hour capacity, while AGMs can accept 100% and in some cases more, flooded batteries are limited to 25%, hence the 25% rule of thumb).  That is, the alternator output required for this battery bank, in order to achieve reasonable re-charge times, should be at least 250 amps.  Continuous duty alternators of this capacity are available, however, they are not inexpensive and their installation requires careful engineering and often fabrication of heavy duty brackets.  Custom pulleys may also be required to fine tune the alternator’s speed (alternators have a sweet spot, where they generate maximum current while providing adequate cooling from their built in fans; all alternators have a “red line”, a maximum allowable rpm which must not be exceeded) to achieve maximum output at the vessel’s cruising speed.

Not all high output alternators are designed to supply current for an extended duration, to do so they must be able to effectively dissipate internally-generated heat.  Those that are not designed for the task are destined for an early grave.

In some cases, two alternators (either on a single engine or one each on a twin screw application) may be required to achieve the required output.  When dual alternators are used simultaneously, both outputs should be connected directly to the house battery bank, and they must be synchronized so they behave as a single alternator.

After my inspection of the 57-foot cruiser I recommended that the stock alternator be replaced by a continuous duty 200 amp unit (the largest that could be accommodated by this engine’s mounting design without significant modifications) along with a multi-stage, temperature-compensated regulator and a battery bank amp-hour monitor, which would enable the owner to accurately determine how many amp-hours had been used by the bank, which in turn would dictate their re-charge cycle.  Additionally, when at anchor the only charge source was an inverter charger whose charge capacity was 110 amps.  Again, while that may sound like a lot, it’s simply not enough for recharging 50% (common wisdom holds that conventional batteries, flooded, AGM and gel, should not be discharged more than 50%, doing so will diminish the total number of amp-hours derived from the bank over its life) of this bank’s capacity, at least not in a reasonable time period.  This was augmented with two additional 100 amp chargers, for a total of 310 amps during the bulk charge phase.  Because the bank was made up of AGM batteries, in theory it could have supported three times this amount of charge capacity.

The vast majority of batteries, particularly sealed valve regulated versions, AGMs and gels, suffer an early death thanks to improper charging regimens.

With this gear in place, as well as a little training regarding battery bank monitoring and discharge protocols, the perceived need for a larger battery bank evaporated.

Although the error was no doubt unintentional, the builder of this vessel never should have installed a mega-battery bank knowing it would be serviced by a mini-charge source.  Battery banks, particularly large ones, must always be treated as an integrated package whose design is based on the electrical needs of the vessel/crew, the desired quiet ship time, and the charge source.  Failure to treat each leg of this battery triangle equally nearly always results in a system that fails to live up to expectations.

Alternator Regulators

While the integration of this system is vitally important to its efficient operation, there are a variety of details and ancillary items that must also be considered.  Among the most important are the methods by which the alternator or alternators are regulated.

As mentioned above, all alternators are not created equal.  Most are designed for short duration high output scenarios, to recharge a start battery or perhaps to supply power to an air intake post heating system for the purposes of reducing smoke upon start up.  The solution is to utilize an alternator that’s designed for extended high output operation.  That, however, is only half of the high output charging equation.  Alternators of this variety are long on brawn and short on brains.  While exceptionally robust and capable of delivering amps galore, they typically lack regulation of their own and proper regulation is especially important when it comes to recharging a large battery bank as quickly and as safely as possible.

Smart, three stage, temperature-compensated regulators are the heart of a high output charging system and large battery bank.  Without them, most stock alternators tend to under or over-charge the banks they serve. 

The internal regulator supplied with most stock alternators has a reliable but unsophisticated charge profile or voltage range.  In spite of the alternator’s rated output, when guided by such a regulator, it’s simply not capable of replacing large amounts of energy that have been drawn from a heavily depleted house battery bank, or doing so in a manner that ensures the longest possible battery life.  When called upon to do so, after an initial high output, it often tapers back to a modest charge rate.  The results are twofold.  One, the battery bank becomes chronically undercharged and two, the voltage that the batteries are exposed to is often incorrect, which leads to poor performance and a shortened lifespan.

Fortunately, the solution to the problem is straightforward enough.  In addition to correctly sizing a proprietary high output alternator for the battery bank that is or will be installed, it must be controlled by an external multi-stage “smart” regulator.  Smart external regulators have been available to the marine industry for many years, I installed my first 25 years ago, and even the earliest models represented a vast improvement over what were hitherto available, internal regulators, the vast majority of which weren’t even adjustable.  External regulators pair precision control with a high output alternator’s brute force, offering the user the best of both worlds.

The owner of the most advanced high output charging system is flying blind unless he or she is able to monitor the battery bank’s state of charge, using an amp-hour meter like the one shown here.  Amp-hour meters are every bit as critical to these systems as multi-stage regulation.

The key to effective management of alternator output is to supply it in distinct stages, bulk, which is typically between 14.1 and 14.6 volts, 28.2 and 29.2 for 24 volt systems, acceptance or absorption, usually 2/10 of a volt below bulk, and float, which is typically one volt below bulk.  Each battery type has its own ideal charge profile, for which most smart regulators can be programmed.

Batteries are able to accept different charge rates as a function of their internal resistance, which in turn is a function of their state of charge or SOC.  Heavily discharged batteries have low resistance, and can therefore accept higher current, while nearly fully charged batteries possess high resistance, and therefore accept current more slowly.  This is why replacing the final 10%-15% of a battery’s charge can be a very slow process; internal resistance is high, thereby limiting the charge acceptance rate.

When compared to their conventional brethren, smart regulators are much better able to determine, and take advantage of, these states of charge, tailoring the alternator’s output for the greatest charge efficiency, and thereby ensuring the shortest possible recharge time.

Bulk is, as the name implies, the highest output stage of the alternator/regulator.  It sends a heavily depleted battery bank the greatest possible amperage that it can safely accept (send too much and it will cause the battery to overheat and possibly catch fire).  As the bank’s state of charge increases, the regulator switches to acceptance mode, which is essentially a throttled back charge rate, held at a constant voltage.  Finally, once the battery is fully charged the regulator enters a float mode, keeping the battery bank’s voltage high enough to prevent self-discharge and sulfation (an accumulation of energy-robbing sulfate crystals on the batteries’ plates) and low enough to prevent overcharging.

I don’t believe it would be an overstatement to suggest that multi-step charging protocols have been to large house battery banks what fiberglass resin has been to boat building.  Without this approach, using large battery banks and recharging them in a reasonable amount of time would be virtually impossible.  Absent this level of charge efficiency, convenience and functionality the plethora of DC gear that’s become an integral part of the modern cruising vessel would be impractical.

Temperature-compensation plays a critical role in high output charging systems; it should be considered a prerequisite in any high output alternator or shore charger installation.

Although deemed optional by some, temperature compensation is, in my opinion, an indispensable part of any multi-step smart regulator system.  Because batteries are capable of accepting a higher voltage when cold and consequently incapable of safely accepting the same voltage when hot, temperature compensation plays a vital role in establishing battery charging parameters and increasing longevity.   Simply put, temperature compensation is a must for any multi-stage charging system, whether derived from an alternator or shore-powered charger-inverter/charger.

Shore or generator-powered chargers play an equally important role in properly charging large battery banks when the vessel is not underway.  Inadequately-sized systems lead to extended generator run time, with the nuisance, additional maintenance and maladies that accompany it.

I recently inspected a battery bank that was (wisely) located in the lazarette as the vessel cruised the Bellingham Channel, where the water temperature was a chilly 53°F.  The charge rate was noticeably higher than, say a vessel I inspected the previous month, it was located in the Bahamas, the water temperature was 75°F, and its batteries were stationed in the engine room.  The temperature compensation probe enables batteries living in vastly different environments such as these to be charged safely, efficiently and quickly (or as quickly as possible) while ensuring maximum battery longevity.

Typically, the probe is adhered to the battery case, or bolted to one of the battery terminals in the house bank (the stick-on probes are notorious for falling off, I usually apply a bead of silicone sealant over them to keep them in place.  It’s important that the probe be installed on the house rather than the start bank, as the house bank will be heavily discharged and cycling and it’s the bank to which the alternators’ output should be directly connected.  If the house bank is split between two locations, which is undesirable, the temperature probe should be installed in the location that is anticipated to be hottest, the engine room rather than the lazarette for instance.

Temperature compensation doesn’t stop at the batteries, alternators also benefit from this feature.  This temperature probe  will alert the regulator to an impending overheat scenario, at which point the regulator will reduce the load placed on the alternator.

For vessels equipped with twin propulsion engines, the preferred approach, for maximum charge capacity, calls for the installation of one high output alternator on each engine with, once again, both outputs connected to the house battery bank.  In order to operate properly, however, they must be synchronized using a device that will enable them to act in concert rather than in opposition.  If separate, unsynchronized regulators are used, one of a twin independent alternator set up will often prevail, leaving the other in idle mode, essentially nullifying the value of a twin arrangement.

Some regulators are capable of simultaneously controlling the output of two alternators.  Taking this approach ensures the alternators will always work in concert.  An intervening device may be, but is not always, required, check with the manufacturer of your regulator.  Provisions must be made to disable the field voltage to an engine/alternator that is not running, this may be done automatically, using the aforementioned synchronizing device, or via a manual, or oil pressure actuated, switch.  By the same token, twin high output alternators installed on the same engine also benefit from being controlled by a single regulator.

Depending upon their sophistication, and cost, regulators may encompass additional valuable features.  These include start delay, which gives the engine and belts time to warm up before applying alternator load, as well as preventing the alternator from placing a load on a smaller engine during cranking.  A remote battery sense enables the regulator to measure and compensate for the battery bank’s actual voltage, thereby taking into account voltage drop between the battery bank and alternator.  The value of battery temperature sensing has already been mentioned, however, the same approach can be used for the alternator itself.  By sensing its case temperature, the regulator can reduce the load on the alternator if it becomes too hot.  Finally, a belt management program enables the user to intentionally de-rate an alternator’s output, thereby reducing the load on the alternator and engine crankshaft pulley.  This can be especially useful in small engine applications, where crankshaft as well as belt loads must be managed, or where, for longevity purposes, over-sized alternators are used, a 400 amp alternator for instance, being limited to 250 amps will run cooler and last longer than a 250 amp alternator running without limitation.

All alternators are designed to produce maximum output within a specified rpm.  Ideally, the alternator will reach this sweet spot at the vessel’s cruising speed.  Too much of a good thing can be problematic, however, as over-speeding an alternator will result in its self-destruction, pulley seizure, and engine stoppage.  Make certain you, or your electrician, do the pulley math before proceeding with a high output alternator installation.  This installer failed to ‘do the math’, causing the alternator to overheat and seize.

Advanced alternator regulation is now well-understood, there’s no reason not to take advantage of it; where large battery banks are concerned, regardless of whether they are flooded, gel or AGM, it’s a veritable prerequisite.

Text and photos by Steve D’Antonio

Copyright © 2017

From the Masthead

Taiwan Has Ruined Me

I travel to many parts of the world for my work, domestically as well as Europe, Asia, Australia and South America.  While I’ve had the good fortune to gaze upon land and seascapes whose majesty takes one’s breath away, of all the cultures I’ve encountered Taiwan’s remains unique and among the most memorable.  The regions in this country where I work are anything but picturesque, it’s crowded, industrial, smoggy and gray, yet there’s something about its people that I find irresistibly magnetic.  I write this editorial while in flight, returning from yet another trip to this small island (it’s about the size of Maryland, with a population of 24 million, roughly equal to that of Texas).  With the experience fresh in my consciousness, I’d like to share with readers a glimpse of what I experience while there.

“Made in Taiwan”, it’s a phrase that inaccurately conjures up thoughts in the minds of many that aren’t flattering, inexpensive, cheap, or throw away.  In fact, while Taiwan seemingly is one giant workshop, and steel mill, and while much of what comes out of this land is no doubt mass produced, my interaction with Taiwanese boat builders and related craftsmen has been one of boundless admiration.  If you can imagine, describe, and draw it, they can build it to whatever specification or standard that suits you, including everything from fine teak and cherry cabinetry, to sophisticated electrical systems, precision drive trains, and of course complete vessels.  When I walk through boat yards and shops while there I often marvel at the quality and ingenuity, and what’s more, they almost universally achieve this level of perfection with the simplest of tools, many of which are made by the craftsmen who use them.  In all the trips I’ve made to Taiwan, I’ve never seen a store-bought plane, awl, broom or tool box; all are handmade.  The roll away tool cabinets owned by mechanics in American boat yards could only be dreamed of by even the most skilled, experienced Taiwanese boat builders.  They achieve a great deal with very little.


When I carry out inspections in a Taiwanese boat yard those working there are universally deferential and friendly, most shop floor workers speak little or no English.  On virtually every occasion on which I crawl into the recess of an engine room or lazarette, flashlight in hand, within seconds a Taiwanese worker appears with a drop light and a smile.  They know I’m there to critique their work, yet they are helpful.  Most yard owners and managers are eager for constructive criticism, and virtually all the staff I encounter are sponges for knowledge and learning new and improved techniques.  I often think to myself, ‘if they came to an American boat yard to inspect the work we do, would they get that sort of treatment’?

Night street markets are, by the way, not to be missed.  The country is essentially devoid of violent crime, and now that I ponder it, I’m not sure I’ve ever even heard a raised voice in public.  Taiwanese are simply too busy working or studying, it seems, to descend to this level of unproductiveness.


This attitude does not stop at the shipyard gate; it universally permeates Taiwanese culture, from those working in airports and hotels, to restaurants, airline cabin crews (the national airline, China Airlines, is in my top three favorites) and taxi drivers.  In the latter case, every one I’ve encountered, without fail, has been professional and courteous, scrupulously honest, endeavors to get you to your destination as quickly as possible (always wear your seatbelt) and every cab spotless.  When they pull up to a curb drivers literally run from their door around to the trunk to unload your luggage, and if you beat them to it they look genuinely disappointed (I’ve learned to walk slowly).  They neither expect nor rely on tips; however, if you provide one, and I always do, they are likely to shake your hand, bow or salute.  When they send you off, whether it’s at the airport or a train station, it’s as if you are being dropped off by a family member, they always wave, and flash a big smile, and while few speak English, some say a well-practiced “Have a nice trip!”


Service nationwide is orders of magnitude beyond anything you’ve probably ever experienced in Western cultures.  Even those doing the most menial jobs, washing windows and mopping floors for instance, take their work seriously and give it their maximum effort, running, as noted previously, is the norm for hotel clerks, and bell hops.

Taiwan’s high speed train, on which I can travel nearly the length of the island, about 200 miles, in 90 minutes, is staffed by some of the most squared away transit workers I’ve ever encountered, anywhere.  Their precision, and uniforms, complete with white gloves, leather pouches slung across their chests, and sharp creases, would put many of the world’s armed forces to shame.

Taiwan’s people have, therefore ruined me in many ways; I’m forever measuring service and attentiveness against this impossibly high standard.  They are a tough act to follow, and a culture in which I very much enjoy immersing myself.


Photo Essay: Exhaust Temperature Alarms



Most vessel operators, and many professional mechanics alike, believe that the first line of defense against an engine overheat scenario is the engine’s own audible overheat alarm.  While the coolant temperature gauge, and audible high temperature alarm are no doubt critical components, by the time the latter sounds, there is a good chance damage has already occurred, either to the engine itself or the water-cooled portions of the exhaust system.  Engine blocks possess significant mass, and as such it takes some time for the coolant temperature to reach a point where it will trigger the alarm.  By the time that happens, if cooling water has been interrupted by a blocked seacock or strainer, it often means the exhaust system has been operating without cooling water for several minutes.  While that may not sound like a lot, consider that the normal temperature of the wet exhaust is somewhere around 150°F, while the dry, uncooled diesel exhaust can range from 400°F to 1,000°F.  That sort of heat will very quickly turn a normally water-cooled exhaust hose or fiberglass pipe into toast, which can in turn lead to thousands of dollars’ worth of damage, or worse, lead to a fire.

A wet exhaust temperature alarm will alert a user to this sort of impending scenario long before any damage occurs.  In some cases vessel operators have reported to me that in the process of cleaning a strainer they inadvertently left the seacock closed.  Anyone who has ever done this knows, in addition to feeling very foolish, it nearly always results in a cooked impeller.  In most cases the helmsman is alerted to the oversight when the engine’s high temp alarm sounds, at which point he or she no doubt thinks, “I can’t believe I did that!”  For vessels equipped with exhaust temperature alarms, this scenario is all but eliminated; it reacts so quickly, typically within 30 seconds, and it’s threshold is so low, usually around 165°F, that no damage is done; in most cases even the impeller survives unscathed.

When I mention the importance, it’s a requirement for ABYC compliance, and value of a wet exhaust temperature alarm, some skippers, those whose vessels are equipped with raw water flow alarms, believe it’s unnecessary, but they ignore its importance at their own peril, and here’s why.  Consider this especially insidious and potentially disastrous scenario, one I’ve encountered on several occasions; the raw water hose between the engine’s heat exchanger outlet and exhaust injected elbow parts or slips off its pipe to hose adapter.  Because the engine is still receiving cooling water, it doesn’t overheat, the flow indicator registers no problem, and no alarms sound, all the while seawater is being pumped into the engine room, and possibly spraying onto the engine.  The first sign of trouble is often the sounding of the high water alarm, if the vessel is equipped with one and it’s working.  The wet exhaust temperature alarm offers the greatest protection against a range of failure scenarios, including this one.

There is one additional nuance worth mentioning when selecting or evaluating a wet exhaust temperature alarm, which involves the placement of the sensor.  In order to ensure the most rapid reaction time, the sensor, which should be a quick-acting thermistor, must be strapped to the exhaust hose immediately downstream of the injected elbow.  However, some installations, particularly those installed by production boat builders, rely on a sensor that is screwed to the metallic injected elbow itself.  While this is better than no sensor at all, most injected elbows are made up double wall pipe, with the void between them normally filled with seawater.  If the water supply is interrupted, however, that void is filled with air, which is a poor conductor of heat, which in turn delays the alarm from being triggered, as it takes longer for the metal’s temperature to reach the trigger point.

Under no circumstances should the sensor pierce the hose, or be exposed to directly to seawater.   Such an arrangement, if it fails, could lead to the introduction of atomized seawater and exhaust into the engine room, a catastrophic occurrence if ever there was one.  This is entirely unnecessary; a sensor strapped to a hose will react rapidly and last far longer.

In the accompanying images are examples of both the hose (top) and metallic injected elbow-located sensors.   The former is not only more effective, it uses a thermistor, it’s easier to install, it’s simply strapped in place.  Because most do not include a self-test feature, wet exhaust alarms should be tested at  least annually using a heat gun and infrared pyrometer, with the sensor being heated until the alarm sounds, and the pyrometer registering the temperature at which it was triggered.  Power for exhaust temperature alarms should be drawn directly from the engine’s ignition circuit, to ensure they are passively active whenever the engine is running.

Ask Steve


In your Ask Steve column you had a reader requesting a way to get the last little bit of water out of the bilge, wouldn’t a system such as the Arid Bilge be a better choice for really dry bilges?

Thank you,

Dan Winchester


The Arid Bilge system is effective at removing small amounts of water from shallow bilges without bilge wells, where a conventional bilge pump will not work.  I have no reason to believe using it in an application like the one included in the ‘Ask Steve’ column wouldn’t work, albeit at comparative high cost, with greater complexity, and with a larger foot print, when compared to a conventional low profile bilge pump like the one I recommended.  The Arid Bilge claim to fame is its ability to remove virtually every drop of water, whereas even a small self-priming bilge pump is likely to leave some water behind, albeit a small quality.

A few years ago a client inquired about such a bilge drying system.  I asked him why he believed he needed it.  His response, “Because there’s always water in my bilge” gave me pause.  I knew the vessel well and I could think of no source of water that would lead to a perpetually wet bilge.  I suggested he have a technician come aboard and carry out a thorough check of the raw water plumbing before investing in the bilge drying system.

I received a call a week later, in which he revealed the source.  During the refit a technician had used a high zinc-content red brass close pipe nipple for the air conditioning raw water discharge fitting.  Brass with a zinc content greater than 15% should never be used for raw water applications, this one lasted roughly eight months before it corroded and sprang a leak, several actually, whenever the air conditioning ran it behaved like a miniature sprinkler.  When it ultimately failed, the vessel would have flooded rapidly.

The moral of the story applies to any bilge water, regardless of the pumping system; identify the cause before dealing with the symptom.


Hi Steve,

We have corresponded before and this is a question about dripless stuffing boxes. After reading your recent article on dripless stuffing boxes I thought I would write you about my experience with them to see if any of your readers or you have had the experience I had.

I have a 1984 Jersey 40 with cat 3208 300HP engines and 1 3/4 inch shafts. When I first got the boat I had dripless stuffing boxes installed and I had a lot of problems with vibration. After having the props worked on and the shafts checked I was told it was the stuffing boxes, the shafts have a fairly long run that is unsupported. I removed the dripless stuffing boxes and put the old ones back (packing type) the problem seemed to stop but I still had some vibration. Finally I took the props to a prop shop that had the latest technology in prop tuning and balancing and the problem went away.

Do you think that the problem was a prop problem and I could put back the dripless stuffing boxes or do some stuffing boxes act as an intermediate support?

I do not see any indication of wear or rubbing of the shaft in the stuffing box and it runs nice and cool even after many running hours.

Thanks for a great column.

Jerry Marmer


When it comes to shaft support, formulas to calculate the required bearing spacing are available in the ABYC Standards.  Barring the use of those, the rule of thumb is as follows, supports should be no further apart than 40 shaft diameters (and no less than 20 shaft diameters), which in this case is 70 inches.  If the distance between the shaft coupling and the bearing is greater than this distance, then shaft whip or vibration is not uncommon, and it sounds as if that’s what’s occurring.  Because of its rigidity, it’s possible that your conventional stuffing box was acting as a support, stifling vibration or whip.  If the stuffing box is rigidly mounted, without a hose as some are, then this is almost guaranteed, and such installations are considered supplemental support.

The fact that the vibration was eliminated or diminished after the props were reconditioned is encouraging.  However, I would not consider returning to the dripless stuffing boxes if the distance between shaft supports or bearings exceeds the above-mentioned formula, as it’s likely the conventional stuffing box is providing a measure of support, and keeping shaft whip under control.


Hi Steve,

I attended your spring Trawler Training workshop, which was great by the way, and thought I would touch base with you on this.

This past weekend I had an unfortunate encounter with a submerged uncharted rock that damaged one of my props on my 1999 Azimut 46. After the boat was hauled and the yard manager took a look he asked if I knew anything about the discoloration of the props. He said it looked like a “halo” effect possibly from heat treating or corrosion. I’ve only owned the boat for a little over a year and nothing was ever mentioned about them. I purchased the boat from the original owner. Can you tell anything from these pictures?

Appreciate any insight you may have.




Ouch…operating vessels without keels places special burdens on navigators.  I hope the repairs weren’t too costly.  On the bright side, whatever the cost, if you had pods you probably could have tripled it.

I love a good metallurgical mystery.  Unfortunately I don’t believe this is one of them (and once cast, bronze propellers are not heat treated per se).  If this were a corrosion issue the metal would be bright and clean, and pitted, and that doesn’t appear to be the case.  If I had to hazard a guess, based on the photos alone, I’d say it’s a mild case over-zincing, which is a bit like the opposite of corrosion.  In that case, an alkaline solution is formed around protected underwater metals, which can cause this sort of discoloration.  It’s not harmful per se (other than to aluminum and timber vessels).  If you were concerned, it could be tested and verified by a (preferably ABYC certified) corrosion technician using a reference electrode and a multi-meter.



What is the best way to deal with a shore power receptacle that does not match our cord?

We have finally arrived at a marina with power. But the receptacle is a different configuration. Should we have a marine electrician change the end on our power cord??

I read in a boaters blog that “serious boaters” (not sure who that is or is not) often have a junction box at the end of their shore power cord, and then wire the local plug fitting to the junction box.

Is this feasible? Advisable? Dealing with high voltage is daunting….

Thanks for any guidance here…

Ann Evans


Chilean shore power is 240 volts 50 hz.  Are you going to supply this to the whole boat?  If so there are a slew of caveats that go along with doing this.  The primary issue is the 50 Hz frequency, not everything you have aboard can run on it properly including refrigeration, some compressors and motors.  Some HVAC compressors and systems are designed to operate on either frequency, others are not.  Of those that do, some specify that when running a system designed for 60 Hz on 50Hz the voltage needs to be reduced as well.  While many users report being able to run household appliances designed for 60 Hz on 50 Hz with no issues, other than clocks running slow, you do so at your own risk, many manufacturers prohibit it and failures do occur.  Again, there are many issues to consider.

To answer your question, unless you are comfortable wiring the adapter then yes have an electrician either changer your cord end or preferably make an adapter.  For the latter he or she will need a local male plug and a North American 50 amp 240 volt female plug, this is really the preferred option, because you can then wire any other male plug to this “pigtail” .

I wouldn’t go the junction box route. As noted above I’d simply have a female plug that plugs into the male end of your shore power cord.  Into that plug you can then wire any local male plug, which will then be your adapter.


Text and photos by Steve D’Antonio

Copyright © 2016

Photo Essay: Boiling Water with Batteries


A few years ago the thought of boiling water using battery power would have been scoffed at, a crazy notion that simply defied logic or the technical capacity of the systems available at the time.  Today, however, it’s far from unusual, along with powering just about anything else you can think of via batteries and inverters, including air conditioning.

Inverters have been commonplace aboard cruising vessels for twenty-five years.  Of late, however, their capacity has grown in leaps and bounds, thanks in no small part to the increased popularity of household solar arrays, wherein larger capacity is a necessity.  Now, a 5 kW inverter arrangement is common, and 15 kW systems are on the rise, supplying 120/240 volt power to the vessel’s entire electrical panel with the exception, perhaps of the water heater (where it’s possible but simply makes less sense).

The image shown here was taken aboard just such a vessel, equipped with a 240 volt inductive range, operating solely on power supplied by the battery bank and inverters.  Designing vessel electrical systems to operate air conditioning units, both split and chiller systems, from inverters, typically while underway but on battery power as well, has also become relatively common.  The first such system I worked on was completed 7 years ago, and it was quite unique at the time.  Today, it hardly raises an eyebrow.

While the inverter capacity was the key to the growth of these systems, it should still be thought of as a package.  The battery bank must be appropriately sized, along with its charge capacity, as well as alternator output, regulation and wiring, and all of this gear must be adequately ventilated to prevent overheating.  Ultimately, however, it’s now doable and relatively straightforward.

 Ask Steve

Hi Steve,

Since your inspection I decided to take out the 10 year old insulation in my engine room and replace with new Soundown foam/rubber/Mylar and a thick damped aluminum facing.  I think it’ll look great, last longer and smooth out the chopped up areas in that engine room.

While removing the ceiling and forward bulkhead pieces, we found fiberglass thermal insulation. It wasn’t in great shape – dark splotches, packed out and torn up.

My thought is to replace it with high R polyethylene panels from Home Depot. No mold, easy to install and maintain their R rating forever.

Any reasons why I should get some “marine” version if there is such a thing or will the home stuff be fine?

Hydraulics – I decided to change all the steering and A/P hose on the boat. Another thing that’s 10 years old, has cracks and is not flexible. In looking over the lines, I found the steering lines are actually copper from the power pack about half way through the engine room. They aren’t secured really well and are kind of old and bent up.

From there, they flare into the hoses and run up to the two helms.

I was thinking of replacing it all with SS tubing. Instead of spending the money on new hoses that will just get old again, the SS will look great and last forever. Any negatives to that?  It’ll cost more than just new hoses obviously!

Another question:

Engine pre-oiler- my mechanic told me about this system and it really appeals to me. Simple way to pressurize the internal oil galleries etc. before engine start, heavily reducing initial wear on the engine, which is when most occurs.

Side benefit is that you don’t have to pour oil into any filters when changing them. Just wipe the gaskets, screw them on and flip on the pre-oiler, which will fill the filters.

I haven’t seen the actual design of the system but I don’t think it’s complicated – maybe a couple of small pumps and switches.

Btw, we are plumbing the fuel polisher to do the same thing for the fuel system. We will be able to change a fuel filter and not have to purge the system manually, but rather will push an electric button.

One of the mechanics told me I should filter the coolant but I think that’s going a bit too far for my application!

Paul Weismann


While there isn’t a specific requirement regarding fire retardant materials for insulation in recreational vessel engine rooms, after all wood and fiberglass are flammable, the less flammable surface material that’s used in an engine room the better.  If you used this material, facing it with something flame retardant would be preferred.

While stainless steel tubing would be the gold standard for hydraulic plumbing, it’s costly and in this case unnecessary.  Copper tubing is commonly used for hydraulic steering with good reason, it’s durable, reliable and corrosion resistant.  I’d replace the hoses and keep the tubing, make sure it’s well supported and can’t move when the hoses move.  If the hoses are made up with plated steel ends, as is commonly done, be sure to corrosion inhibit them using CRC Heavy Duty Corrosion Inhibitor.

The engine pre-oiling concept is one that’s been around for decades.  Your mechanic is correct, it makes sense, however, in a recreational application it’s difficult to justify, as the engine isn’t started that often.  I can’t recall the last time I encountered a recreational diesel that died as a result of plain, simple bearing wear.  The liability with pre-oilers is they represent more plumbing, and more potential for failure, in the high pressure oil gallery.  For a launch, on the other hand, which is being started dozens of times a day, the marine equivalent of a UPS truck, a pre-oiling system would make sense.

A fuel polisher that can be used to prime filters, however, is well worth the effort and offers little if any risk.  Finally, some engine manufacturers, Cummins for instance, includes coolant filters.  In addition to filtering coolant, they include an ablative pellet that maintains the proper balance of corrosion inhibitors.  While it wouldn’t hurt, if you monitor your coolant using test strips every few months, and have it analyzed annually, it’s unlikely that a filter will add significant value.


Dear Sir,

I completely agree with you that radio communication has completely and utterly changed the sport of offshore sailing.  When I was a young man boats were wood, sails were cotton and sailors largely were competent seamen.  You want to sail?  First, crew for someone experienced for a couple of years (for many this was their father).  Then, your first boat would be a small one design, something between a Penguin and perhaps a Comet or Snipe.  Later perhaps moving up to a Lightning or Star.  Only then, after a few years of experience, seasoning, and learning to shoulder the burden of command, would someone turn to offshore sailing where the entire learning cycle would be repeated, but in larger vessels and deeper waters.  Nearly every man followed this model, including  Ted Turner and Dennis Connor;  the only major sailor I can think of who did not was Richard S. Nye, skipper of Carina.

Over the next six or seven decades the expanding economy, fiberglass construction, and electronic communication have all conspired to drastically change sailing and especially offshore sailing, sometimes for the better, but often not.  Fiberglass is much stronger than wooden construction and no one wants to return to cotton sails and manila cordage, but where today is the incredible beauty that came from the boards of Alden Rhodes, Stevens, Hunt, and so many others?  Why do the voyages and books of Slocum, Pidgeon, the Hiscocks, Guzwell and the Pardys so inspire the reader that he prefers to read them over and over and forgo modern voyages where the author was harbor bound for two weeks awaiting an airlifted part for his engine…watermaker…GPS…air conditioner?  Where instead of heaving to on the offshore tack until dawn, he simply turns on the satnav and radio and lets someone talk him into a strange harbor in the middle of the night.  How inspiring is a tale told by a man in a storm offshore who, when the bilgewater is around his ankles and rising, reaches not for a bucket, but a transmitter?

No one would buy a plane, climb right in and take off with no experience or instruction of any kind, but many will do this with a boat.  Several years ago I met a couple who confided they wanted to buy a sailboat and “take off.”  I advised them to purchase a pair of Lasers and learn to sail and race them while they were working and saving for their voyage. Clearly, they didn’t want to hear that.  No doubt they’d rather have purchased something like a Hunter 40, read “Sailing For Dummies,” and cast off.

I’m probably just a grumpy old man, but I clearly remember that cruising on a Hinckley Sou’wester six decades ago was so enjoyable in large part because you were cut off from the rest of the world.  No phone, newspaper, television or radio.  Just the sun and stars, wind and water, and each other.  Comfort was a full stomach, a dry berth, and the knowledge that tomorrow would bring a new port and a new adventure.

So long ago…

Paul J. Nolan

Dear Paul:

Your commentary conjured up long-forgotten memories of the path I took, in developing the skills I needed, navigation, boat handling and seamanship, to safely make offshore passages.  Nearly all began with taking small steps, inshore day passages progressed to longer, multi-day inshore passages, which progressed to offshore passages.  Learning how to read a chart, and dead reckon progressed to (mostly) mastering celestial navigation.  Reading about the passages of others, as you mentioned, is yet another invaluable learning tool.  Along the way I learned the argot of the world of boats, the sea and navigation, a necessary and important, and today all too often overlooked, step in this journey.  I implore all existing and aspiring boat owners to learn and use proper nautical terminology, starting with deck, bulkhead and overhead, rather than floor, wall and ceiling.  For the benefit of Marine Systems Excellence readers, a ‘ceiling’ is the inside part of the hull that can be seen from the cabin, rather than what’s over one’s head.

While I’ll confess, I don’t long for wood, hemp and cotton (well, maybe at a classic boat show), I welcome a dry berth and good hot food, there’s simply no excuse for skipping essential steps when developing critical seamanship skills.


Hi Steve

I’ve read your articles on this topic of engine loading and longevity with interest, as well as other articles on the subject and I’m somewhat confused.

There seems to be disagreement around what ‘loading’ actually means.

Some use RPM as a surrogate, others refer to the manufacturer’s rated power curve, fuel consumption at a given RPM as a surrogate for power, and also the propeller power curve. Tony Athens at Seaboard Marine categorically states (with 30 years of engine repair to back his opinions up) that marine diesels should be cruised at under 50% of rated power but you state that a diesel engine should be run at “80% of its output capacity for 80% of the time”. And you carefully explain the consequences of low-speed running. And yet others state that low-speed running is fine so long as the engines are at the manufacturer’s recommended operating temperature.

My boat has a semi-planing hull with twin 270 hp Cummins 6BTA engines and can achieve full RPM (2600) with full fuel and water tanks and other cruising gear on board (suggesting it is properly propped). At 1600 RPM I’m doing 10 to 10.5 knots (no adverse currents etc) while burning 3.5 gallons per hour per engine. This equates to 70 BHP (26% of maximum rated power) per engine using a standard fuel burn rate of 20 gallons per hour per horsepower whereas my RPM from the Cummins rated power curve equates to 197 BHP per engine, or 73% of rated max power. Also, the Cummins charts show that 1600 RPM equates to a fuel burn of 3.8 gallons per hour in their standardized testing; pretty close to my 3.5 gallons per hour.

I’m sure there is a simple explanation for these discrepancies but since it’s such an important topic for those of us with diesel engines who want to reduce our carbon footprint – and our fuel bills! – but not ruin our engines by underloading them, I hope you can illuminate the topic with your usual clarity and wisdom.

Thanks for your help with this.

Chris Sherlock

Dear Chris:

This is a subject that never stops generating questions, and that’s a good thing.

The 80-80 rule is a rule of thumb, and far from etched in stone.  It wouldn’t apply to many, but not all engines )and it presumes the boat builder has selected the proper size engine, something that seems to be a rarity these days, far too many vessels are over-powered, particularly those of the full displacement variety).  Hard running can be problematic for them.  I know and respect Tony’s expertise and experience.  However, where planing vessels are concerned, for instance, limiting continuous operation to 50% would, if nothing else, lead to some very dissatisfied boat owners, and may put the boat in the half on-half off plane, something that’s always to be avoided.  And, after all, why pay for all that horsepower if you can’t use it?

The way power or load is measured isn’t as critical, it’s an estimation for the most part.  Electronic engines include load and throttle position indicators, simplifying life for mechanics as well as operators.  In the absence of these, however, a rough estimation of power can be derived from rpm and the engine manufacturer’s power curve data.

The correct operating temperature issue can be deceiving as well, as it depends a great deal on what temperature is being measured, coolant, oil, or exhaust gas?  Coolant will nearly always be at the right temperature as it’s thermostatically controlled.  Oil however, except in some rare cases, isn’t (some engines rely on a closed cooling heat exchanger, which essentially keeps oil at or near coolant temperature, which is ideal).  When chronically lightly loaded, oil tends to run comparatively cold, under 180°F.  When it does operate in this chilly region it is much more likely to generate sludge and then varnish deposits, both of which are harmful to engines as they can block oil flow to bearings, cylinder walls, rings etc.  Exhaust gas, when “cold”, under 500°F has its own host of issues, including carbon/soot build up on valves, rings and turbos, which again impedes oil flow, and clog rings thereby promoting blow-by and oil consumption, all of which can also affect efficiency.  In catastrophic cases the piston rings and turbocharger will become impacted with carbon, and there will be predictable lubrication failures, resulting in piston and liner scoring when the rings finally seize in the pistons, and can’t move to accommodate normal thermal cycling.  Modern electronically injected engines can offset some of these issues by avoiding over fueling, however, they can’t make exhaust gasses hotter and they can’t warm up oil (unless they are equipped with an jacket water oil cooler, otherwise if the engine isn’t loaded enough to produce sufficient heat to warm up the oil to the ideal 180°-225°F then the oil will remain cool).

The bottom line is, many engines will be under-loaded on both displacement and planing vessels, particularly the latter when at displacement speed.  The best alternative approach in these cases involves periodically, 10-15 minutes out of every four hours, operating the engine at higher load, high enough, somewhere between 50% and 75%, to get the oil and exhaust gasses into the ideal range.  You can measure oil temperature using an infrared pyrometer on the side of the oil pan.  For testing purposes, in the absence of an exhaust gas pyrometer, you can carefully measure a section of the dry pipe exhaust immediately after the turbocharger.  It will be cooler than the actual gasses, but not much.  Once you have that reading at a given rpm, it should remain constant, negating the need to measure it again.


Thanks so much for this very clear explanation of the issues. I can now operate my boat with an understanding of what is actually happening in the engines. I do have an infrared pyrometer so I will follow your advice regarding measurements while under way.

I heartily encourage you to keep up your strong advocacy on behalf of us boaters for excellent practices in boat building and maintenance. You are doing a great service to the entire industry – even though they may not appreciate that right now!





I love your column. I am looking for a little pump that will suck up that last qt. of annoying water in my bilge especially in a little aft compartment which seems to be lower in the water than the main bilge pump can access.

Bruce Adornato


For bilge “drying” you have two options.  One, use a remote, displacement, self-priming pump.  This sort of pump is mounted well above any water, with a hose that leads down into the lowest part of the bilge.  A strainer or “foot valve” is installed on the end of the hose to catch debris and to direct the suction as low as possible, enabling more water to be removed.

The second option is to use one of the new low profile submersible pumps.  These are centrifugal, rather than displacement, and thus are not self-priming, however, that’s doesn’t matter because their pick up vents are so low they can suck up water much like a self-priming pump.  Whale Pumps makes a nice version called the SuperSub.

The remote mount, self-priming pump can probably be coaxed to get more water out of a bilge, especially if there’s a small well, so if that’s your goal I’d go that route.  If ‘most but not all’ meets your needs, then go with a low profile, centrifugal submersible model.


Text and photos by Steve D’Antonio

Copyright © 2016

From the Masthead

Have you tasted the tea lately? masthead

About two years, in order to make time zone transition easier, I gave up drinking  coffee.  I frequently traverse multiple time zones, my record is 27 in ten days,  making it challenging to get restful sleep.  Sleep experts have noted that caffeine hinders time zone acclimation, and since forgoing it I’m forced to agree.  Additionally, it’s tough to get coffee in some places, particularly in China.  My morning ritual involved drinking a cup while reviewing e mail.  When in Asia I began to find myself fretting the night before about where I would get my cup of joe, and more worrying was the acquisition of milk, which is even more scarce than coffee in China.  Thus, I’ve taken to drinking decaffeinated tea (I was a tea drinker until getting married, at which point my wife indoctrinated me into the coffee drinkers’ cult), which is easy to carry, and I drink it neat.

In making the change I’ve made an interesting discovery, much of the hot water offered for tea, particularly in the US, has a distinctive stale coffee taste.  It simply ruins the tea flavor and is virtually undrinkable.  The reason of course is the hot water is dispensed from urns that once contained coffee, thereby tainting the taste of whatever they hold thereafter.    What I wonder, however, is how those serving it, in hotels, in flight, at airport lounges and elsewhere, could be unaware of this glaring tea faux pas, unless of course they never taste it themselves, which brings me to the marine industry analogy.  When I review invoices prepared by the marine industry, particularly boat yards, I often find myself wondering how they could not know that what they are producing is virtually unintelligible. I also can’t help but wonder if those preparing this material read and critique not only the content but the format as well, which, once again, is often the epitome of illogical and convoluted.  To be fair, having worked on boat yard invoice formatting, it’s impossible to please every customer, however, it is possible to clarify and simplify invoices to make them more understandable to the layman.   The problem of course is those creating these invoices can’t see the forest for the trees, being so close to it, and knowing subject matter so well, often makes it difficult to recognize the flaws, and of course there’s the natural unwillingness to admit fault if they are responsible for the format’s design.

If you agree, then the next time you receive such an invoice I strongly suggest you share it with the proprietor of the organization responsible for it, let him or her know what you don’t like about it and why, and say, “Imagine if you received an invoice like this from someone you’d hired to undertake a task about which you knew little, roofing or furnace repair for instance, what would your reaction be?”.  Figuratively speaking, suggest they take a sip of their own tea.

This month’s Marine Systems Excellence column covers the subject of engine drive belts, I hope you find it both useful and interesting.




Notched belts are well suited to small diameter pulleys.  Using them reduces the likelihood of belt overheating, which is caused by rapid flexing of conventional belts.

The belts that drive an engine’s accessories, which include the raw water pump, circulator pump, and alternator, as well as perhaps a refrigeration compressor and even a hydraulic pump, will typically offer reliable trouble-free service, provided the system is properly designed, and components are maintained, adjusted and replaced before they reach the end of their service life.


While nearly all belts are installed either by adjusting a driven pulley’s position, an alternator or pump for instance, or by compressing a self-tensioning device, some like the one shown here (upper right) rely on “rolling”, where the belt is simply stretched over a pulley by rotating the latter.

Many vessel operators neglect this all too important component, however, waiting until disaster strikes.  Once a belt breaks, all of these vital systems grind to a halt, literally.  The raw water pump stops pumping seawater, the circulator pumps stops circulating coolant and the alternator no longer produces electricity.  For engines that use multiple belts, the failure of one usually spells the demise of the others, as the flailing deceased belt often entangles with, and takes down, the others in the process.  While you may not immediately notice the loss of an alternator, you will very quickly become aware of the loss of seawater and coolant circulation as the temperature gauge climbs into the red, and the overheat alarm sounds (have you confirmed that your coolant high temperature annunciator works, it should sound or chirp each time the key switch is turned on, and you have a wet exhaust high temperature alarm as well, right?).


A properly selected and tensioned belt typically runs at roughly the same temperature as the engine’s coolant,  between 175°F and 200°F.

Belt Types

The belts used to power these accessories are either the V variety, or the ribbon-shaped flat serpentine style.  While V belts were the standard for decades, I clearly recall, as a young mechanic, the day when marine engine manufacturers first began emulating the automobile industry by adopting serpentine belts, it was truly exciting in a gearhead sort of way.  From a mechanic’s and do it yourselfer’s perspective, serpentine belts are very attractive in that they are more robust and reliable, one belt is typically all that’s needed, they are far easier to replace; and most are self-tensioning.


While most serpentine belt-equipped engines rely on an automatic tensioning device, some smaller models continue to utilize the alternator’s adjustment for tensioning purposes.

V belts, on the other hand, have their idiosyncrasies, often, multiple belts are needed, one may do double duty, sending power from the crankshaft pulley to both the alternator and circulator pump, while another belt may be used to turn a raw water pump.  Generally speaking, unless a serpentine belt is used, conservative installations will resort to double V belts (for the most part matched belt sets are no longer used, as the manufacturing tolerances of higher quality belt manufacturers makes this unnecessary), when amperage exceeds 100 amps at 12 volts, or 50 amps at 24 volts.


A Gates “Krikit” belt tension gauge, which enables users to apply proper tension to V belts.

Belt Service

Ordinary V belts are, with a little special knowledge, easily serviced, adjusted and replaced.   “How tight should my belts be?” is almost certainly the most commonly asked question for those carrying out service and replacement.   One dockside rule thumb calls for one half inch of belt deflection for every foot of belt span between pulleys, sometimes referred to as sheaves (rhymes with cheese).  The problem with that approach is the deflection varies with the force that’s applied, and with no means of measuring that force the formula is of little use.  Fortunately, a tool does exist for this application.  Called the Kriket™, and made by Gates Rubber, it takes the guess work out of tensioning V belts.  It’s readily available on line and at many auto parts stores, and is useful for both professionals and boat owners alike (I find pro’s tend to overtighten, while boat owners under tighten belts).



Belt dust, which is frequently generated by misaligned belts, is extremely fine.  In addition to distributing itself over the front of the engine, it’s also drawn into the alternator, where it is deposited, and interferes with heat dissipation, as well as the engine’s air intake.

An under-tensioned belt will slip, and a slipping belt won’t turn its related accessories properly, it will overheat, wear out and break prematurely.  An over-tensioned belt will accelerate wear on driven accessories’ bearings and seals.  In addition to tension, alignment is another issue that must be dealt with.  An accumulation of belt dust on the front of the engine or the alternator casing and fan, it’s often so fine and “greasy” that it’s mistaken for an oil leak, is nearly always an indication of a misaligned belt.  Because it is so fine such dust is nearly always drawn into alternator windings, to which it adheres and hinders heat dissipation.  Misalignment is a common occurrence in the case of after-market high output alternators, where support brackets are either improperly designed, or where they lack the necessary rigidity to prevent flexing and distortion when belts are tensioned.


Belt engagement is critical, particularly on highly loaded components such as high output alternators.  The rule of thumb for these is no less than 120°.

Shedding of belt chips, or chunks can be a sign of a heavily loaded belt that lacks sufficient pulley engagement or tension, which can cause the belt to skip; this is also especially common on high output alternator installations, where belts should engage pulleys for a minimum of 120°.

Loose belts, they create an unmistakable squeal, lead to glazing or polishing of the pulleys’ belt interface surfaces, overheating, and plasticization of the belt, all of which accelerate slippage.  If the belt and/or pulley show signs of glazing, a particularly smooth, shiny, and in the case of the pulley an almost chrome-like appearance, it’s a clear indication the belt is slipping. A chronically slipping belt will lead to overheating of the pulley; in extreme cases it may turn purple, which in turn can damage an alternator; extreme heat will travel through the pulley shaft and into the rotor, upsetting the magnetic field, and preventing electricity from being produced.


Slipping belts overheat rapidly, which leads to glazing and plasticization.  Belts suffering from such damage must be replaced, and their pulleys carefully inspected for glazing. New belts installed on glazed pulleys will slip once again, and quickly suffer the same fate.

While an overheated, plasticized belt must be replaced; the glaze on a pulley can be removed using 220 grit Emory cloth, which is used to “dress” the glazed surface, returning it to a slightly rough, satin rather than high gloss finish.  If a new belt is installed on a glazed pulley, it will almost certainly slip, recreating the original problem.


Large diameter pulleys engage the belt over considerable surface area, making slippage unlikely even when belts are under tensioned. 

Where small diameter pulleys are used a notched V belt may be needed.  Small pulleys are often used to increase alternator rpm on slow-turning diesel engines.  Conventional belts can over heat as a result of rapid flexing associated with turning over these small diameter pulleys.


Many serpentine belt systems rely on an automatic or self-tensioning pulley.  Most utilize a square recess, one can be seen here in the center of this image, into which a socket drive or breaker bar is inserted, which in turn is used to compress the spring for belt replacement.

With very few exceptions serpentine belts are self-tensioning, eliminating the most common cause of premature belt failures.  A spring loaded tensioning pulley places just the right amount of pressure on the belt to keep it from slipping, while preventing over-tensioning.  In order to replace a serpentine belt, however, the installer must have a means of compressing the considerable tension exerted by this device’s spring.  This is often done by inserting a ½” drive socket wrench or breaker bar into a square recess in the tensioner’s arm and levering it into the compressed position (and holding it there while the belt is installed, some use a lanyard for this purpose, however, use caution, the spring tension is extremely high, never place your fingers between a belt and pulley).  Without this tool it is virtually impossible to carry out a belt replacement.  Additionally, unlike Most V belts, whose routing is intuitive, most serpentine belts take a circuitous, counter-intuitive path through and over accessory, idler and tensioning pulleys.  Therefore, make certain you make a diagram or take a photo of the installed belt before the existing belt is removed or fails.


This serpentine belt is suffering from both wear and tear, as well as a worn tensioning pulley.  The latter is evidenced by the white filament visible on this belt, the result of misalignment induced by the worn tensioner.

At each replacement, be sure to turn the idler pulleys, as well as the tensioning pulley, each should spin freely and smoothly, without excessive resistance, creaking or squeaking; any of the above call for replacement.  A desirable belt replacement practice involves replacing all belts while dockside, under ideal conditions. Doing so will ensure you have the correct tools and belts. Once complete, save the old belts as spares, as you can be certain they fit.  Many a skipper has been caught unprepared because a spare belt, even one supplied by the engine manufacturer, did not fit.  Be sure to rotate your stock of spare belts and other rubber and soft goods, such as impellers, as these deteriorate storage.


A laser is being used here to confirm proper belt alignment for this alternator, one of three on this engine.

For heavy duty applications, particularly high output alternators, and where maximum life is desired, consideration should be given to using extreme duty belts, both in the V and serpentine variety.  Gates offers a range of belts called FleetRunner™ which are designed for use in ambulances, fire engines, military vehicles and other critical equipment.  Identifiable by their unique green color, they are my belt of choice, and are well-suited for marine use.



Demanding applications require heavy duty belts.  The Gates FleetRunner series, available in both V and serpentine style, used on ambulances, emergency and military vehicles, is well suited to marine high output alternator applications.  Compared to conventional belts, they are thicker and include additional reinforcement.

Belt Fit and Tensioning

Ensure that each V belt’s profile properly matches every pulley over which it turns.  The belt should be even with or stand slightly proud, no more than a sixteenth of an inch, of the top of the pulley walls.  Belt’s whose diameter is too large ride too high on the pulley groove walls, reducing the contact surface area, while belts that are too narrow ride in the bottom of the groove, causing them to teeter, reducing the tension on the groove walls.


Serpentine belt routing is often anything but intuitive, be certain you have a diagram or photo of yours before undertaking replacement.

Serpentine belts come in different widths as well, typically measured by the number of grooves or ridges they possess, which must match those on the mating pulleys.  Ideally, when fully tensioned, a V belt’s tensioning device, an alternator or pump, should be roughly in the middle of its adjustment range.  Most serpentine belt tensioners are marked to indicate their allowable range of motion, which is a function of belt length.  In a very few cases, some smaller serpentine belts used to drive a single device have neither an adjustment nor a self-tensioning wheel; instead the belt is designed to be “rolled” onto the pulley, allowing it to stretch and then retract into place.  Make sure you know if your engine is equipped with one of these, and that you understand the replacement procedure.


The handle of a hammer can be used to push an alternator or pump away from the crankshaft pulley, thereby tensioning the belt for adjustment.

To tension a V belt use a suitable prying mechanism, the handle of a hammer works well for small engines, while a crow bar may be needed for larger applications, as a lever to push the accessory away from the crankshaft pulley, and then tighten the fixing bolt.  Threaded “spreader” bar tools are available to make this task easier, and some aftermarket high output alternator installations incorporate this into their design.  Keep in mind, smaller driven pulleys (found on nearly all alternators) offer less belt contact area, making correct tension all the more critical; loads are high and slipping is a constant issue.  Larger pulleys, on the other hand, like those used for many raw water pumps, offer more contact area, making tension less critical; loads are usually low and they rarely slip.



This belt is too wide for the pulley its driving, the belt stands substantially proud of the pulley, and it fails to make contact with most of the pulley wall, which can be seen by the wear pattern that is too high up the grove wall.  Ideally, the wear pattern should be centered on the pulley wall.

Belts should be inspected regularly (don’t forget the ones hidden under belt guards and generator enclosures), look for evidence of glazing/slippage, guard interference, plasticization, cracking, dust production and improper tension.  Where serpentine belts are concerned the appearance of belt filament, white threadlike material on one side of the belt, is often an indication of misalignment, which is typically the result of a worn tensioning pulley.  As it wears, it tends to force the belt to one side of its own pulley and the downstream idler pulley, causing excessive wear.  A squeal can also be associated with this phenomenon, as the belt is being “wiped” over a smooth, non-grooved idler pulley.  When this occurs, many users simply change the belt, however, doing so will only yield a repeat performance; the problem can only be resolved permanently by replacing the tensioner.


This belt is far too narrow for its pulley, it’s riding in the bottom of the groove, where contact is limited.

Belts are comparatively inexpensive, and thus it makes good sense to replace them every 2 years or 500 hours, whichever comes first.  Remember, a new V belt may require adjustment and retensioning several times in the first 50-100 hours of use; watch for dust, glazing, squealing and chip shedding.   For dust and chip shedding, be sure to clean up the fall out after making corrections, so you’ll know if the problem has been resolved.