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Top tags: Boat Wiring  E-11  AC and DC electrical system  Boat Battery  Corrosion  Corrosion Protection  Electric Shock Drowning  Electrical systems  ESD  Exhaust System  Label wiring on boat  voltage drop 

Cathodic Over-Protection

Posted By Ed Sherman , Monday, August 20, 2018

Back around July 4th I was asked by an old friend to look over three very expensive antique wooden boats that were just beginning to show some strange activity in the bilge areas of the boats. Keep in mind here that these weren’t a collection of derelict wooden junk heaps ready for the scrap pile, but three classic yachts that had undergone multi-million dollar restorations and that were now working in the high end charter business.

The photo above, although not from one of those boats,  illustrates some of the similar activity that was occurring on those boats. Unfortunately this is an all too common scene when I inspect wooden boats and left unattended, this can destroy a boat. What you see here is the early stages of wood delignification, and the process is also taking a more obvious toll on the bronze fasteners you see turning green. When the wood delignifies, all of its inherent strength is lost!

The problem here is cathodic over-protection, which on a wooden boat is really, really easy to achieve quite innocently, which is why I’m writing this. You see the ABYC standard E-2 that addresses cathodic protection identifies appropriate levels of cathodic protection for various hull configurations and materials. Basically the standard calls out negative voltage ranges appropriate for these boats. In the case of wooden boats, the range is -550 mV to -600 mV. therein lies the issue. You see depending upon the anode material you are using, which could be an aluminum alloy, zinc, alloy or in extreme cases in really clean fresh water magnesium anodes, the negative potential achieved by the anodes can easily exceed the potentials these alloys typically achieve. Voltage potential is a value that is achieved by adding or subtracting the amount of anode surface area when compared to the metal area we are attempting to protect. So indeed, we are creating a controlled electro-chemical reaction. The problem with wood is that the value that is considered safe is a mere -50mV. It is almost impossible to maintain that level of protection over the course of a normal boating season in a salt water environment.

So, sure enough, when I tested the three antiques they were all reading in the -900mV range. That amounts to approximately 300 mV overprotected. The only way to reduce that number is to reduce the exposed surface area of the anodes to the seawater on these boats. As I left the dock, the owners had divers down removing anodes and retesting the voltage potentials. I hope we caught it before excessive damage occurred to the wood on these otherwise beautiful boats. In my view, boats in this category should invest in a permanently installed impressed current cathodic protection system engineered to deliver the proper voltage potentials under all conditions as the needs do change if the boat is docked, underway, or the water chemistry changes. Various companies can design and get installed such a system. In the long run, these systems will be much less expensive than sending divers down monthly to service the anodes on your classic wooden yacht.

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Shore Power Can Be Lethal

Posted By Ed Sherman , Wednesday, July 11, 2018

It seems like people seem to forget that 120 volts can be lethal. The photo below was sent in by one of my surveyor friends. The photo was taken aboard one of the boats he surveyed recently.  There are several glaring errors with the boat owner installed AC receptacle shown.

First, the green screw you can clearly see is there the safety grounding wire should be connected. This is the connection that can help provide electrical shock hazard protection in the event of a fault within the plugged in appliance. Not going to happen with this install…….Additionally, the receptacle must be inside an approved, UL rated box to comply with ABYC standards.

Don’t think that just because the backside of an AC switch or receptacle is facing into a space where it appears no one will be likely to come in contact with the live terminals on the device. For the price of a $2 UL approved plastic box a patently unsafe installation has been created here. The cable used is ROMEX single strand household rated wire. Again, NOT compliant with MARINE standards.

 Another shot for my shop of horrors collection of photos!

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How To Properly Label The Electrical Wiring On Your Boat.

Posted By Shannon Aronson, Tuesday, January 30, 2018
Updated: Tuesday, February 6, 2018
How to Properly Label Wiring on Boat


What’s the best way to label the wiring on your boat?

 The photo below shows one person’s take on this, use a sharpie and write on the wire insulation to tell you what the cable is for. Certainly this is something I see fairly often on new boats right from the factory and the bottom line is that it actually meets the ABYC E-11 standard.

But, I would suggest that this may not be the best approach to take. One, its pretty hard to write clearly on a piece of 14 AWG wire in a legible fashion, two, if the wire ever gets re-terminated, part of the description will probably end up going missing; as you can see in the below photo the writing is right next to the crimp connector on many of the wires shown.

My personal preference on new boats are printed heat shrink labels. These get purchased in sheets and are actually run through an old DOT matrix printer. As long as they don’t get shrunk into place too close to the terminal, re-termination will not impact the label. I’ve seem paper labels used and they simply don’t hold up. 3-m does make some paper labels that get sealed with a transparent plastic overlay once you write what you what on the label.

Again, as long as the label isn’t too close to the end, all is well. Pre-printed numbers on heat shrink tubes are also a good choice. Just make sure to provide a decoder chart that tells what wire # 23 is for. You get the idea. Just remember, ABYC E-11 offers broad latitude for identifying the function of DC conductors. For AC wiring, it’s best to strictly follow the internationally accepted colors, black or red for “hot” wires, white for neutral and green or green with a yellow stripe for grounding or “earthing” conductors.

Tags:  Boat Wiring  E-11  Label wiring on boat 

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Excessive Voltage Drop & Your Boats Electrical System

Posted By Ed Sherman , Tuesday, January 30, 2018

One of the things we are concerned with on boats is excessive voltage drop. This is especially true with your boat’s DC electrical system, typically 12 volts. With only 12 volts to start out with, a loss in voltage can have a really profound effect on how your DC appliances operate.

This is most important for things like your electronic equipment, navigation lights and bilge blower circuits on gasoline fueled boats. In fact, the ABYC dictates that a maximum drop of only 3% of nominal voltage is allowed.

Excessive voltage drop is caused by things like loose connections, corrosion, or sometimes by wire used in a circuit that is too small a wire gauge to handle the amount of amperage the appliance in the circuit needs to function properly.

Symptomatically, excessive voltage drop will show up as an engine starter motor that is not cranking your engine fast enough, or lights that are glowing too dimly or a fish finder that is blinking diagonally lines and other forms of mishmash on the display screen. Remember, if voltage drop is excessive, inadequate amperage is flowing through the circuit in question. Both volts and amps are closely related.

The third key player in this mix is resistance, measured in ohms. We’ll talk more about ohms in a later installment, but understand that all three of these components must play together well, and the truth is, on a boat, they often don’t. I’ve used the diagram below, which was first used in one of my very old Cruising World articles on this topic, to explain the interaction between volts ohms, and amps.

So, looking at the diagram above. Think of volts a pressure, amps as rate of flow, and ohms, well you can see what he’s always trying to do, especially on your boat. With more pressure, you can actually distribute high amperage through a smaller pipe (wire), but if voltage is a constant, and too low, amperage is just not going to get through the ohm guy. OK, so now lets see how to use your voltmeter to measure something besides how much voltage your boat’s battery has available.

In the diagrams below, I’m showing you how to measure voltage drop at different points in a starter motor circuit. In this case the symptom is slow cranking. You’ve already tested the battery and you know it is in good shape, and up to charge.

In the above example, the meter is set to the DC volts scale. The black lead from the meter is connected to your battery’s negative terminal and you are tracking through the circuit with your red lead. You are looking for a voltage reading of something in the order of 0.1 or 0.2 volts at any given point in the circuit. The measurement is the amount of voltage drop in that particular leg of the circuit. It is cumulative, so if you want to truly isolate a given leg, put your negative lead on one side of the starter button and the positive lead on the output side of the starter button and depres the button. A voltage reading of greater that 0.2 volts tells you that the starter button switch has too much resistance through it, causing excessive voltage drop. Your slow cranking problem could be caused by the switch itself. A well connected starter circuit with everything in good order should not have a cumulative voltage drop of more than about 1 volt with the engine cranking. This methodology will work on any electrical circuit.

Measuring Amps

With amperage, its nice to know ahead of time what the normal current draw is for a given circuit. Some electrical appliances will give you this information, it’ll be on a label on the appliance somewhere. (Actually required on AC appliances). The appliance might only tell you the operating voltage and the wattage of the appliance. That’s OK, because with those two bits of information, you can easily calculate the third bit you need. A water heater for example might be rated at 120 volts, 1500 watts. By dividing the watts by the volts you can derive the amps needed to run the appliance at its maximum potential. 1500 divided by 120 equals 12.5 amps. OK, but what if you turn on the heater and clamp the AC hot wire (black wire) and measure less than 12.5 amps? Whats implied?

Here’s where your thorough understanding of all of this becomes important. There are several possibilities here and you will need to decide which it is. The water heater above may only be rated to 500 watts, or the cable supplying the unit is too small to carry the amperage required. If its neither of those two things, it is possible the heater element is faulty, in which case the element will need to be removed for further inspection. The tables below show some typical requirements for popular on board appliances, both AC and DC. Use these as a rough guide. These tables come from two of my books, The Powerboater’s Guide to Electrical Systems and Advanced marine Electrics and Electronics Troubleshooting. 

Tags:  AC and DC electrical system  Electrical systems  voltage drop 

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How To Winterize A Boat With A Waterlift Muffler

Posted By Ed Sherman , Tuesday, January 30, 2018

My Yanmar diesel is equipped with a waterlift type muffler in the exhaust system but it has no drain in the base of it. I’ve been told by ABYC Certified techs that a drain is required under the ABYC Standards, but my boat doesn’t have one. Do I need to worry about this?

Answer: The ABYC Standard that addresses exhaust systems does require a drain for this type of muffler. That said, I’ve seen plenty that don’t come equipped with one. You have several options here. One is to remove the muffler and drill and tap a drain fitting into the lowest section of the cylinder that you get to conveniently.

If you opt for this approach, be advised that the wall thickness on the muffler may not be adequate to support tapping threads into effectively. I can see from the photo you sent in that the muffler is made of spun fiberglass and not high temperature plastic like others I’ve seen. Those units do not have adequate wall thickness to tap threads into I can assure you. Yours may. If not, since it is fiberglass, you could drill a hole, and add some thickness by epoxy gluing a small 1/2″ thick piece of delran or similar plastic sheet to the outside of the canister and then drilling and tapping it to accommodate an appropriately sized pipe plug to facilitate draining each year.

If all that seems like more than you want to tackle, you can winterize the exhaust system by warming up the engine and then removing the raw water intake hose and running the boat engine while pouring a potable anti-freeze solution through the raw water cooling system.

Once you see anti-freeze tainted cooling water being pumped out the exhaust pipe, you will be all set as far as a potential freeze-up in the exhaust is concerned.

Tags:  Exhaust System 

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Does Your Boat’s Wiring Meet ABCY E-11 Standards? - Ed Sherman

Posted By Shannon Aronson, Tuesday, January 30, 2018
Updated: Friday, June 15, 2018

One of the areas I get an occasional question on has to do with what you see in the photo below. You are looking at the backside of a fairly typical electrical panel. What you see is three rows of standard two pole circuit breakers and the master wire harness coming in from the top side with all of the DC positive conductors attached.

On the opposite poles you see some neatly bent uninsulated single strand copper wire that connects all of the other poles on the circuit breakers. At each circuit breaker the installer has carefully made a solder joint attachment to the 5/16″ male spade terminal protruding from the breaker. All very neat and tidy.

The question however is whether of not this complies with ABYC Standards. The answer is no. Not so much because of the single strand copper, I consider that as nothing more than a “custom” buss bar. Its probably better than the brass bars you often see used on cheaper panel arrangements, since copper is far more electrically conductive than brass.

The problem here is the beautifully hand-crafted solder joints on the terminals. The ABYC E-11 standard is quite clear that “solder shall not be the sole means of electrical connection”. Crimp and then solder yes. Straight solder. NO.

Too bad, because this looks sort of elegant and my bet is it’ll last for years just as it is. But, that’s just my vote. The ABYC electical PTC (project technical committee) said no to this arrangement somewhere along the line. Not sure if they were really thinking of this sort of arrangement. I understand the reasoning behind the requirement, if the terminal were to overheat it could actually melt the solder and cause a disconnect. Also, the solder really doesn’t have the physical strength. I get that too.

My thinking here is that if it got that hot behind the panel,  the boat owner would have bigger worries. As for the strength properties, I just don’t see where its needed in this particular installation. I’d love to hear your comments on my thinking here! So, send them along.

Tags:  Boat Wiring  E-11 

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Electric Shock Drowning (ESD) What You Need To Know

Posted By Ed Sherman , Tuesday, January 30, 2018

I spent a day with some marina managers and maintenance personnel conducting a class on how to check for and minimize the possibilities for electric shock drowning, or as many have now begun calling it simply, ESD. Much has been written about ESD over the last few years and it is finally getting the attention of the general public and perhaps more importantly, conscientious marina operators.

One of the points made that took a bit of explaining to the attendees at my session was how these faulty stray currents can actually enter the water from a boat that is made of fiberglass, actually a pretty good insulator of electricity.

It’s all about the grounding system on a boat that is built to ABYC standards. Both the DC and AC electrical ground circuits on board the boat are connected at one point on the boat, what we refer to in standards as “the engine negative terminal or its buss”.

Now, if the boat also has a bonding system, whereby all of the underwater metal components are tied together via a green wire for the purpose of corrosion mitigation, the bonding system, which is also connected to the engine negative terminal or its buss, becomes the point at which fault currents can start leaking out of the boat into the water. T

he amount of current will vary greatly depending upon the condition of the dock’s ground system but given a faulty device on board and a less than ideal ground system on the dock and more current will leak out of the boat into the water its floating in. Some of my archived articles on this topic cover the whole human risk factor here quite well. (Do a site search here for ESD or In water shock) One of the pertinent questions asked by one of the maintenance folks at my session was what the common causes of ground faults on boats are.

Three Common Causes Of Ground Faults On Boat’s are:

Well the photo above gives the number one fault away:

  • In my experience electric water heaters in my experience are the number one cause of ground faults.
  •  Number two? Old battery chargers where the internal insulation breaks down and the shore power side of the unit starts to leak over to the DC side trying to charge your batteries.
  •  My number three most common cause is a neutral to ground bond at a point in the boat’s electrical circuitry other than a source of AC power. These are most often created by land based electricians doing what they have been trained to do in land based electrical installations. This should never be done on a boat.

The only AC neutral to ground (connecting the white wire to a green wire) connections on board are made at generators or inverters, and then only when they are invert mode. Additionally, if the boat is equipped with an isolation transformer, then the boat side of the transformer becomes a new source of AC power and therefore a neutral to ground link is established.

The mistake the land based electricians will often make is to link the neutral and grounding buss bars behind the main power distribution panels on the boat. This simple error will create a situation where as each AC appliance gets turned on, more and more current from the appliances that would normally return to its source via the neutral conductor gets dumped into the boat’s grounding system.

Combine that with a bit of not so great dock wiring and the current enters the water via a through-hull fitting, creating a potentially lethal situation for swimmers near your boat.

The lesson here? Keep your cousin Vinny the licensed electrician away from your boat’s AC wiring until he gets some training on MARINE electricity. My shameless plug? Make sure the person working on your boat’s electrical system is ABYC certified in electricity.

Tags:  Electric Shock Drowning  ESD 

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Wire and Water Don't Mix

Posted By Ed Sherman , Tuesday, January 30, 2018
Updated: Tuesday, January 30, 2018

OK, so you are probably wondering what’s going on in this photo (see below). Well it’s part of a little experiment I conducted over the recent holiday break. I had been working on an article for Cruising World magazine that was related to hidden damage to boats that may have been damaged and ultimately “totaled” by the insurance company down in the Caribbean this past fall. The crux of the article was what hidden damage there may be that could make a great deal on a damaged boat look like not such a great deal. In my research for that article I came across some information about a test that one of the surveyor groups conducted some years ago trying to find out how far up an insulated wire water might migrate if either end of the wire were exposed to sea water. Grab a copy of the 2018 DIY issue to read that article entitled “Trouble Lurks in Wet Wiring”. The bottom line is that I had some time to kill and decided to try testing this potential problem myself. So, the three pronged plug and 30″ of wire you see in the above photo is the result of my little experiment. You can clearly see the white fuzz surrounding each of the three conductor terminals on the plug assembly shown. This was the end of the wire that was NOT submerged in salt water. This plug and cord was just cut off a failed appliance that I had in my test area. I stripped the wire insulation off one of the three conductors and just left the other two with a clean edge from the cutting pliers.

So, after four weeks you see the result of the test. The moisture from the salt water I had submerged the cut-off end of this length of cable into managed to migrate via capillary action up the entire length of the 30″ length and managed to exit around the terminals. So, what have I learned? If submerged in seawater for any length of time you need to be concerned that this migration will travel along the individual strands of copper wire and ultimately cause some pretty extreme corrosion!

Tags:  Boat Wiring  Corrosion 

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Corrosion Protection, What Are the Numbers?

Posted By Ed Sherman , Tuesday, January 30, 2018

One of the questions I get periodically is what the correct numbers should be when checking a boat for appropriate levels of cathodic protection. Or, written in proper lay terms (totally inappropriate technical terms): “So, what should the numbas be if I want to make sure my boat won’t get attacked by electrolysis?” Its a good question and deserves a proper explanation. My lead photo shows some typical numbers for a fiberglass boat with classic stainless steel propeller shaft with bronze propeller along with some bronze through-hull fittings. The range of protection, measured in millivolts, and oh yes these are negative numbers, is -550 to -1100mV. This value will vary depending upon the boat configuration. Wooden boats for example have a protection range of -550 to -600mV. An aluminum boat would have a range of -900 to -1100mV. The imperative thing to remember in all of this is that these numbers come from the ABYC standard E-2 and are based on measurement in SALT WATER at a specific speed and temperature range. Therein lies the potential problem. What if the boat is located in fresh or brackish water in a fast water current area where the water temperature is typically colder? What should the numbers be then?

Well, there is no standard answer to this question. I can share some experiential data, but the reality is this must be handled on a case by case basis. Also, understand that in some areas, this will be a moving target that depends on a variety of environmental factors.

Checking in with one of my ABYC certified technicians located in northern Michigan, where the water is fresh and typically cold, and using a silver chloride reference cell (Ag/AgCL) He says that boats in his area rarely experience corrosion problems and that their anodes last multiple seasons typically. When testing potentials, he tells me he gets readings in the -300 to -400mV range using the silver chloride reference electrode and aluminum anodes. My own test with fresh water gave me a reading of -363mV. Understand that this value can change depending on actual water chemistry and temperature.

As for brackish water, the numbers can cover a much broader range. In my experience, in the -500 to -700mV range. The reason for this is that you will be in a coastal area where there are more contributors to the water chemistry equation. Run-off from the surrounding land is a major factor. Things like petroleum from highway run off, and fertilizer from farmlands abutting the shoreline are contributing to a really interesting blended soup that can change from day to day depending on the weather. Remember that the run-off, primarily some variation of fresh water will stratify at the surface of saltwater.

So, the question becomes what is a technician supposed to do?  Well you will need to establish your own very localized benchmarks. I’ve always told people in classes I’ve conducted that a boat must get tested where it is actually going to be berthed. That’s one point. Additionally, keep in mind that in many coastal areas boats actually migrate from their berthing areas to other water chemistries on a daily basis, further complicating these issues. For boats doing that, I typically recommend an impressed current system that actually measures hull potential and adjusts its output in real time. This is the perfect, if not a bit expensive solution. For other less frequent migrators, I recommend protecting for the location where the boat spends most of its time.

So, once a technician has established a baseline for the water they are dealing with, there is one key statement found in the ABYC E-2 standard that applies. “A minimum negative shift of 200mV relative to the corrosion potential of the least noble metal being protected must be maintained.” Keep in mind that Table 1 in the E-2 standard is also based on a saltwater premise. So, typically numbers will be less negative for each of these as well depending upon the actual water chemistry. Keep that in mind when you are trying to figure out the 200mV differential.

Tags:  Corrosion Protection 

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Batteries and Wood Don’t Mix

Posted By Ed Sherman , Tuesday, January 30, 2018
Updated: Tuesday, January 30, 2018

I discovered on a boat this year something that I find all too common on newer boats and that is battery(s) sitting directly on wooden surfaces. This certainly flies in the face of ABYC standards which require that batteries be installed in a dedicated area that is made of materials that won’t e attacked by any electrolyte from the battery. Now in the photo above several issues are immediately evident to me. One, the battery is sitting directly on a wooden surface. Two, the locker the battery is in is by no means dedicated, so its quite likely that other gear is going to get shoved into that space. Depending upon the gear, it could induce a short circuit between the positive and negative posts on the battery or in the worst case maybe even crack the battery case causing an extreme leak of electrolyte into the boat. As for this install, one could argue that the battery is of the sealed variety and therefore electrolyte is unlikely to leak out causing damage. Every time that argument comes up at an electrical committee meeting, the counter argument is the same, yes, but what if someone decides to replace the battery you see with one that has open, serviceable cells? Not too far out of the realm of reason I would say. Remember, the USCG nor ABYC offer any special breaks for sealed or AGM or Gel type batteries in their installation requirements for that very reason, who knows what will get installed once the battery you see gets replaced? Keep batteries in dedicated boxes with covered terminals and if you must use wood, paint it with epoxy to seal it from any acid exposure.


Tags:  Boat Battery 

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