ABYC Online Education "Huddle": Discussion and Review of Popular Technical Topics with Mike Bonicker
What this covers
ABYC’s Lead Instructor Mike Bonicker and Education Director Dave Broadbent review the key questions that come up in some of ABYC's most popular online training courses, touching on bow thruster installation, electric shock drowning, AC dock pedestal testing, and more.
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Proper installation, maintenance, and testing of marine systems—bow thrusters, shore power pedestals, seacocks, and outboard/stern drive corrosion protection—requires specialized knowledge of electrical sizing, structural integrity, and cathodic protection to ensure boat safety and prevent catastrophic failures.
- Bow thruster installation demands structural fiberglass expertise and careful positioning; undersizing the motor or poor cable sizing creates operational and safety problems
- Electric shock drowning in freshwater is a critical safety hazard caused by poor grounding and bonding; testing AC pedestals reveals dangerous ground faults before incidents occur
- Corrosion on outboards and stern drives is primarily a maintenance problem, but requires understanding of anode systems, coatings, and bonding isolation rules to prevent catastrophic metal loss
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Bow thruster electrical systems draw very high amperage (brief but intense draw) and can cause significant voltage drop to other boat systems if run from the main battery bank, causing electronics to lose power when the thruster is keyed; this problem is prevented by installing a dedicated battery near the thruster with its own charging system.
“the biggest issue with not installing a dedicated battery is that uh you know these units have a it's brief usually fairly brief uh but very high amperage draw um and i have seen i've been a party to a couple of instances where um depending on how the boat is set up uh one of them was a very large hatteras an older hatteras and every time they they keyed the key to bow thruster the bolt drop would be so much that the uh the electronics would blink out and most electronics will go out you know the voltage gets below 11 and a half”
ABYC standards require two hose clamps on only two specific applications: flexible exhaust system component junctions and fuel fill hose connections (both at the deck fitting and at the tank); double clamping is NOT required on seacocks or most through-holes per ABYC rules, though ISO European standards differ.
“one of those uh misconceptions of uh the requirement of two hose clamps on the through all that is under avyc standards that is not a requirement iso european standards you will see some european boats that do have two hose clamps on a c-cock because that is an iso standard but there are only two places that abyc requires uh two hose clamps one is on a flexible exhaust system component uh junctions uh and the other is on fuel fill both at the fuel fill um fitting on the deck and at the tank”
Even with a good shore ground connection, a ground fault aboard boat will still send some current into the water through the AC/DC grounding connection to the engine, propeller, and shaft because there are two current paths, not a single return path.
“so you can see even with a good ground um with a ground fault we've got we're going to have two paths you know because of because our ac is connected to our dc connected to this engine connected to the shaft um no matter what some of that fault current is going to go into the water even if we have a good ground back to shore”
Bow thruster installation requires someone adept at fiberglass structural work because cutting large holes in the boat hull and glassing the tube in properly is essential to avoid the tube coming loose in the future.
“one of the main issues is having someone who is adept at fiberglass structural fiberglass work uh the the cutting of the hole”
Shore power at AC dock pedestals should be tested to confirm correct voltage (120 or 240V), frequency (60 Hz), absence of stray current (ground faults), and proper grounding, because poor ground systems in marina wiring cause many electrical problems on boats.
“one is you know especially if you're troubleshooting or have an issue on the boat you got to confirm that you have at the pedestal what you think you have uh that you have 120 or 240 volts that you have 60 hertz uh but then you're also looking for things like um straight current uh in in that and i mean in the short cable in the system um and whether or not the you have a good ground uh that you know there are there's a a lot of issues caused by poor ground systems in marina wiring”
Electric shock drowning incidents in marinas most commonly affect children or swimmers in freshwater, and when bystanders see someone struggling, they often jump in to help, inadvertently placing themselves in the same electrical hazard—the correct emergency response is to shut off all dock pedestals in the vicinity before attempting a water rescue.
“the biggest issue is that um it tends to be kids now you're talking about people swimming in the water around the boat um or you know heaven forbid yeah i hate to see anybody swimming in a marina you know it could be around a boat with a generator run um but in a marina especially you never want to see anybody swim in an arena especially if it's fairly fresh water but when it happens people on the dock think hey that that kid or that person is drowning so what do they do they jump in to try to help the person and find them find themselves in exactly the same situation”
Backing plates for through-hull fittings are required when flanged seacocks must be bolted to the hull per ABYC rules; they are typically composite fiberglass plates bonded to the inside of the hull to provide attachment points without drilling additional through-holes, or older installations may use threaded machine screws on the exterior that are sealed and hidden under bottom paint.
“the only thing that things this doesn't show is that flange seacock is required to be attached to the hull uh those holes you see should have bolts in them one way of complying with that is by using one of the backing plates that it's a composite fiberglass backing plate that is made to accommodate bolts for specific size through-hull and then after the bolts are put through the backing hit plate the backing plate is then bonded to the inside of the hull”
The biggest cause of corrosion on outboards and stern drives is lack of maintenance of the anodes, exacerbated by a misunderstanding that these engines were not originally designed for boats that stay in the water continuously; aluminum requires anode protection and coating to keep aluminum exposed to water, not just anti-fouling coating.
“probably the biggest cause is lack of upkeep on the anodes um and most people's misunderstanding of the properties of outboards and outdrive stern drives um they they really were not originally intended to be on boats that that stayed in the water all the time um you have to have their aluminum uh they have to be protected a with anodes that are kept up on a regular basis they need to have they need to be coated not necessarily with anti-fowling but if the boat stays in the water all the time it should have some sort of anti-falling on it uh but that aluminum needs to be insulated from the water as much of it as possible”
Through-hull fittings and seacocks are required to pass a 500-pound load test per ABYC standards, likely because a person falling from above would generate forces far exceeding body weight, creating a safety margin against structural failure.
“that isn't the standard the 500 pound load test for seacocks so we actually did a test on that that we uh winched with a load cell and actually winched it building this out to test it so it you can test it it's fun uh but yes all those things have to have a 500 pound load test and mike i believe the background if you know i was that if you're falling stepping down there's a lot more weight than whatever your body weight could be that's going to be falling on it so i think that's one of the reasons it's 500 pounds and not just the normal human weight”
Bow thruster cable sizing must account for distance, not just manufacturer minimum specs—a long cable run may require heavier gauge than the manufacturer recommends to stay within the 10-volt-drop maximum, and can be calculated using the circular mils conversion formula.
“the manufacturer will usually spec a minimum size but it doesn't always hold uh hold to the letter because uh if you're in a scenario where you've got to run cable a long distance it's possible that the even the minimum size cable that the manufacturer is recommended uh won't be big enough again it comes down to distance”
Divers cleaning boat hulls underwater receive no protection from electric shock drowning hazards, though the risk is lower in saltwater because they are not significantly more conductive than seawater and will feel only a tingle rather than paralysis.
“if uh if you're i see you know it's it's you see a fair amount of divers around and you see a fair amount of people that do it themselves uh you know it's much less of an issue in salt water uh you're more than likely gonna feel a little bit of a tingle uh but because you're not so much more conductive than the water around you it's not going to be as much of an issue but uh there there is there is nothing there to protect uh from happening if you if you get the water to clean the bottom of your boat”
A 'brow' is a deflection structure built on the front side of a bow thruster tube to redirect water flow around the exposed flat back of the tube, or alternatively, the hull can be recessed on the back side to reduce the hard deflection of water hitting the tube.
“once you drill a hole through the hull the two holes if you were to look at it dead on from the bow uh with the tube in place because of the flare of the bow and how the bow gets wider as it goes back you're going to have a flat spot facing dead forward the back of the tube is going to be facing dead ahead and exposed outside the flare of the bow on the forward edge of the tube so i've seen it done a couple of different ways uh the conventional fairly conventional way is to build a brow it's called a brow on the front side of the tube to deflect water past that flat spot which would be the back of the tube and i've also seen um where they have made cutouts uh a dished it's hard to explain it uh on the back side on the hall from the back side of the tube sort of recessing that area to get it to where the front of the tube is as far as width so that you don't have that you wouldn't have that hard deflection of water uh hitting off the back of the tube it has the ability to slide by as the boat moves forward”
Most modern bow thruster units are completely sealed without oil reservoirs, eliminating the need to check oil levels or inspect for seal leaks, unlike older or larger units which have oil drain plugs and reservoirs positioned above the waterline.
“ones that have plastic liter side power uh they have plastic blades most of them on their propellers occasionally some of the bigger ones have an anode behind the uh behind the blades some of them have a little anode which a lot of people don't know about because it's usually not there on the oil fed systems the one that had the the one that we installed does not have an oil reservoir uh so it does not have a drain plug on it a lot of older units and larger units will have an oil drain plug”
The most commonly overlooked seacock and through-hull maintenance item is exercising (operating) the seacock valve at least once per year to ensure it remains operable, as valves that are not actuated regularly may become stuck and non-functional when needed.
“there's not a whole lot of regular maintenance it has to be done you should always you know periodically check make sure the hoses are decent make sure the hose clamps are okay um if it's a seacock or a through-hall the seacock does not get actuated much which many of them do not um in the spring in the fall maybe you're winterizing you're commissioning the boat uh moving back and forth a couple times uh you get those ones like uh like overboard discharges from heads that never get opened somebody wants to open it it's not gonna open um so exercising the refer to that is exercising a through-hole exercising the seacock sorry uh the through-hole is the piece that goes through the hole the seat is the valve so exercise the valve on a regular basis at least at least once a year that's that should do uh we'll do a lot to to keep the uh keep the valve operable when you want to be able to operate it”
For an outboard that is trimmed up but the lowest tip remains submerged in the water, the best practice is to leave the outboard low enough so at least the lowest anode is in the water, then manage biofouling through periodic cleaning rather than risking corrosion from an unprotected submerged portion.
“you know the big thing is to make sure it's coated if it's if it's properly coated problem is that's where 10 of the where um depending on the design of that of that lower unit but as long as it's properly coated and not just anti-fouling it's got to have a barrier code on it of some sort as long as that area is barrier coded basically isolating the metal from the water then you won't have any problem but yeah the issue happens is that you know the coating wears off it wears through you have exposed aluminum there you're going to have problems if that outboard doesn't come all the way out of the water you know the best thing to do would be to leave it all the way down uh so that the anodes are also in or leave it down enough so that at least the lowest anode is in the water you'd still have to deal with maybe cleaning a little fouling off of it now and then but it would protect the unit whatever part of it's still in the water right”
Bow thruster maintenance is minimal and primarily involves monitoring anodes (zinc or other sacrificial metal) for wear, checking for oil leaks on older units with oil reservoirs, and visually inspecting for corrosion; the anodes are the number-one maintenance item.
“it's not a whole lot of maintenance that has to be done on these they have anodes most of them do uh depending on the construction um ones that have plastic liter side power uh they have plastic blades most of them on their propellers occasionally some of the bigger ones have an anode behind the uh behind the blades some of them have a little anode which a lot of people don't know about”
When a second hose clamp is installed on a small-bore fitting where the barb is not long enough, the clamp may be positioned only at the very end of the barb or even beyond it, which can crush or cut the barb, damage the inside of the hose, and do more harm than good—proper double clamping requires sufficient barb length.
“especially on smaller hose sizes uh there's not enough room that the barb is not long enough to get two hose clamps on and by installing that second hose clamp which is either going to be just on the very end of the pipe to hose fitting the hose barb uh or may even be beyond it it's either gonna crush it uh can cut into it uh the end of the hose barb can cut into the inside of the hose uh so in a lot of cases where they don't fit properly they do more harm than good”
A 37-foot Californian with a flybridge has significantly more windage than a 40-foot Sea Ray (non-flybridge), requiring a more powerful thruster even though both are similar length, because the flybridge design creates additional wind resistance that affects bow thruster effectiveness.
“if you have a flybridge motor yacht 40 foot it's got a whole lot more windage uh than you know a 40-foot sea ray uh something like that so those are the things that that really matter between different power boats”
Electric shock drowning in freshwater and brackish water occurs because these water types are poor electrical conductors (lacking ions compared to saltwater), making the human body—which is mostly saltwater and an excellent conductor—a better conductor than the surrounding water, so current preferentially flows through the swimmer rather than dissipating in the water.
“electric shock drowning is mostly a problem in freshwater areas how it happens why it happens is because either fresh and brackish water to a certain extent are poorer conductors uh much much poorer conductors than salt water is uh you know current we talk about current how does current flow uh current moves by electron movement in conductors but it moves through ions in the water and ions can be you know ions are basically charged particles uh and uh salt is a great ion”
Corrosion protection options for outboards are strictly anodes only, while stern drives typically use a combination of anodes and an impressed-current cathodic protection system (e.g., Mercathode for Mercury, equivalent systems for Volvo); impressed-current systems use battery power to actively protect the metal in addition to passive anode protection.
“as far as outboards it's it's pretty much strictly anodes uh for stern drives uh it's usually a combination of anodes in some sort of impressed current system which is the mercato system and mercury i know volvo has one i'm sorry i can't remember off the top of my head what they call theirs um but uh it's an it's a i don't know how to explain explain or describe it without the getting too deep in it it's actually a a system that's connected to the battery power on the boat which works electrically to produce uh voltage much like the anodes do to help protect the metal even further”
GFCIs trip between 3-7 milliamps (typically 4-6mA), which is below the 15mA threshold for muscle paralysis but intended to interrupt before paralysis-causing currents can develop.
“you can see here uh some measurements of effects of straight current ground fault straight current effects uh one milliamp is a tingle uh most gfcis trip between somewhere between you know three and seven four and six milliamps is the trip uh the fault level uh for tripping a gfci”
Choosing the correct thruster motor size is the most important overall decision in bow thruster installation—for a given boat size, there are typically two options, and selecting the weaker option causes customer dissatisfaction due to poor operational performance, even though both are rated for that boat size.
“really the most important factor is probably the choice of the thruster itself for most boats for most manufacturers that i've seen you will probably wind up with two choices at least as far as particular thruster that you could put in”
When a large hole saw is not available, a jig can be constructed using a rod with a scribed circle attachment to mark the elliptical or egg-shaped hole outline on the hull (not circular due to bow flare), which is then manually cut.
“we had a jig a rod jig made up where once you made your hole on either side uh where it's all been triangulated and you know you have a hole or a center spot at the same point on each side you drill a hole there slide the rod through and it had a jig attached to the rod that would scribe the circle uh on the side of the hull because you're not dealing with uh the shape of what you cut out is not actually round uh because you're you're dealing with an angled it's not all in the same plane it gets a circle uh but it's a circle across a diagonal so the jig would allow you to scribe essentially a circle but once you actually scribe the hole or scribe the lines it was not circular it's more egg shaped or oval depending on the flare of the bow”
Bow thruster installation typically takes 3–4 days once materials are in hand, but can extend to a week depending on factors like whether the yard has a large hole saw (which significantly shortens the process), electrical cable routing complexity, and whether a separate battery must be installed with its own platform.
“once you have the materials in hand um you know it's probably it's probably a three to four day job in most cases you know if the yard or whoever has a crew to get on it and stay on it and do it as long as there's no pitfalls along the way”
For dual outboards, the negative terminals of the batteries should be connected together to prevent potential differences between the outboards, and ideally some bonding between the two outboards themselves should be established to eliminate additional issues, though Mike acknowledges limited personal experience with dual outboard systems.
“any special grounding rules for dual outboards uh there should be the only thing that i would really be aware of there should be some sort of bonding between the outboards themselves uh i am not an outsport expert yard that i worked in we did not deal with outboards a whole lot but it can eliminate some issues if there is some sort of bonding between the two outboards uh other than that you know they're whether they both are fed power from the same battery or two different batteries if it's two different batteries again the batteries uh the negatives of the battery should be connected together um so there's no difference in potential there or between the outboards themselves so uh that's one thing i could say about outboards”
During the Great Catch bow thruster installation, the ABYC team removed all berth and cabinetry from the forward cabin to create an open space, which eliminated accommodation constraints for the tube and motor and also enabled filming; this approach is not typical for customer installations.
“one of the first things we did was just take all the the birth and cabinetry out of the viver uh as a wide open space it allowed us to film we wouldn't have been able to film it otherwise uh but that completely eliminated the issue of uh having to find uh accommodation for the for the tube and the unit”
Marlon FRP (fiber-reinforced plastic) through-hull fittings eliminate underwater metal corrosion issues and are particularly beneficial for aluminum hulls and carbon fiber structures, where they avoid galvanic corrosion problems; they meet specific marine standards and are not simple hardware-store plastic fittings.
“there's their their greatest friend in my practical experience i've had really no problems with them um they you know you've eliminated an underwater metal uh you don't have any any further corrosion issues there uh they're excellent for uh aluminum hauls and if you if you have to add a through-haul to an aluminum hall um and especially carbon fiber uh carbon fiber being graphite is electrically far more noble than just about any other material that you could put in there except for something that's inert like plastic without having to worry about insulating it somehow so carbon fiber halls is where you tend to see them the most um but uh no they are i've seen no longevity issues with them um they are and they are special plastic you cannot just use plastic fittings uh from the hardware store uh these are marlon they are fiber reinforced uh plastic that meets specific criteria and are allowable for use below the water line”
An accidental DC short directly to a bow thruster case dissolved a bronze lower leg in approximately two days, demonstrating the catastrophic failure mode of direct shorts that manufacturers are concerned about when establishing non-bonding policies.
“there's a prime example in there of what could happen when you don't bond uh there was an accidental dc short to the case of the uh of the thruster uh and it dissolved that that bronze lower leg uh in about two days uh it's pretty some pretty dramatic pictures”
Bow thruster tubes are supplied by the manufacturer as part of the unit and ordered specifically for each installation, eliminating the need to source compatible tubing separately.
“when you're dealing with the tube that actually is going to be glassed in where you find a tube like that uh in almost all cases it comes from the manufacturer you order a you order a unit uh and they will they'll supply the correct tube to go along with”
ABYC holds Technical Project Committee (TPC) meetings (formerly called PTC meetings) that are open to the public; participation in standards committees is a good way to understand the reasoning behind safety and installation standards and to contribute to industry best practices.
“and then our ptc meetings will be uh they will be running from january 11th to january 21st so if you have interested in that or have never participated in the ptc uh we're always looking for new members that's the side of the world i came from it's a really cool process and getting to be a part of uh you know keeping boat safe i think it's important i enjoyed it but i got paid to do it but uh i think everyone would enjoy it you can always sit in on meetings so please if you're interested look at look out for that and participate in some of those”
ABYC offers online learning courses on marine systems topics (including bow thrusters, seacocks, and AC pedestal testing) that are available for purchase through their online learning platform; sample content is available on YouTube.
“someone asked where the videos these are actually on our uh like i said they're part of the ibex sessions and these are part of our uh our online learning courses so you can purchase them the idea of today wasn't a sales pitch for it just to try to feed off of that and uh share a little bit of mike's expertise because uh he's out there teaching our classes and all but it's great having him in-house and his experience is fantastic so this is uh we're kind of touching a little bit of everything so if you're actually interested in those we do some samples on youtube but you can actually purchase them on our online learning platform there”
The ABYC's educational boat, the Great Catch (a 37-foot Californian), has a bow thruster installed that was used for training videos and educational purposes, making it a reference platform for ABYC instruction.
“this boat is our educational platform here uh it's our the great catch it's called our 37-foot californian and that's the boat that this is installed on”
A core saw (a type of hole saw used for geological core sampling) was modified for use as the large-diameter hole saw used in the bow thruster installation, likely with a diamond tip, allowing precise and quick drilling of the hull passage.
“where can you purchase a large hole saw for drilling for the bow thrusters that's an interesting one um i believe i remember them talking about that hole saw uh it is a a modified core saw of some sort um i think it was i don't know if it's still a diamond tipped it might be uh i can't remember for sure uh but i've never had to buy one um i would look if you want to look it up they called it a core saw like taking a core sample you know maybe from uh rock or something like that um but that's that's where they modified that hole saw from right”
ABYC's virtual standards week runs from January 5-21, featuring an annual meeting on January 5 with virtual happy hour, PTC meetings from January 11-21 for members interested in standards development, a SureTech surveyor/technician event on January 6-7, and a standards certification course January 26-28.
“we do have our virtual standards week it's stretched out a little bit so we have a save the date out from that so it is going to run from january 5th uh to the 21st uh we have our annual meeting which is going to be january 5th with a little bit of a virtual happy hour so uh please join us for that and then our ptc meetings will be uh they will be running from january 11th to january 21st”
ABYC offers an electrical fast-track certification course shorter than the standard three-week program, designed for those seeking quick certification or wanting to refresh existing knowledge.
“we did just add a new electrical fast track which is a shorter version of the electrical so it's not three weeks i believe it's three sessions uh with some uh some online learning tied into that so if you're looking for a quicker way to get your electrical or you're a little rusty and want to try it again i'd encourage you to take a look at that course”