Electrolysis on my boat.

[Wes_G]

Anyone that knows anything about boat rigging or has had experiences on there own boat with electrolysis I could use your help.

So a couple years ago I noticed what looked like a bit of corrosion happening on the transom of my boat but didn't think much of it at the time. I started to notice a little more water in the bottom of the boat early season last year but figured I just wasn't getting the drain plug pushed all the way in. Then one night after fishing for the day I went out to the garage and noticed a white line down the back of the boat and puddle on the floor of the garage. Took a closer look and there was a hole right through the aluminum. Fast forward to today and I now have 3 small holes all in a similar area with another 2 spots in the paint that look like they are starting as well.

So I have come to learn about electrolysis over the winter and am pretty sure it is what is happening but I can not pin point why its happening or how to stop it. When I play around with a multimeter and put positive to positive and negative to one of these corrosion spots I am getting a reading of 8.8V, same with when I touch it to the anode on the motor and any other bare screw etc.Should a boat have current going through the hull when it is not in use and everything has been turned off?

I took the boat to a marine place in Lethbridge and he added a couple of anodes to the transom as well as installed a master power switch to turn off the power when I am not using the boat. The funny thing is, even when the power switch is off the multimeter still shows current at the mentioned locations. Can anyone do me a huge favor end see if there is current going through there boat hulls when they are not in use?


based on what I have read, I get the impression that this is a far bigger issue in salt water with boats that live in it full time. The couple of boats owners that I have talked to around here have either never heard of it or have no issues of there own with there boats so I am not sure why this is happening to mine. What I think is happening in my situation is that whatever material that they have used inside the transom where the motor mounts to is water logged and the stray current in the hull is causing the electrolysis even when the boat is not in the water, as I have been noticing little drops of water coming out of these holes all winter.

If anyone has any experience of there own dealing with this or knowledge of electrolysis in general could help me out I would be very appreciative. I would like to get this issue fixed before it gets worse. My boat is a 2013 Polar Craft tiller with a 30Hp E-tec. It gets used 20-30 days a year. I have not changed anything electrically in the boat. The company has walked away as they have changed ownership 3 times in the last 5 years and will not warranty anything older then 2018 at this point and even if they would, they do not warranty electrolysis damage.

I can post photo's in a few days if that helps.

[Gbuss]

The only thing i can think of is your motor is putting off a current while in use. If it is mounted directly to the transom steel to aluminum it may cause this. Try to put a rubber gasket between the mounting points on the motor then do your multimeter test.

Gbuss

[Wes_G]

The only thing i can think of is your motor is putting off a current while in use. If it is mounted directly to the transom steel to aluminum it may cause this. Try to put a rubber gasket between the mounting points on the motor then do your multimeter test.

Gbuss


I am definitely thinking it is coming from the main motor. I have disconnected everything else. The current is also there when it is not in use though to. Just sitting in the garage, everything turned off, no key in the ignition, master power switch off, still 8.7V on the multimeter.

[Drewski Canuck]

Can you check if MAYBE someone has attached a ground cable from the battery to the aluminum hull somewhere? People do this sort of wiring on vehicles, but they do not understand that the wiring on a boat only grounds to the battery, and never to the aluminum hull.

Drewski

[Positrac]

Having lived on the coast and been around boats all my life I’ve seen it a lot on aluminum boats. Seldom a purposely place ground but with all the electrical accessories on a boat there are opportunities for it to happen. Scotty made some plugs for electric downriggers back in the very early 90’s that when screwed to an aluminum boat would ground out if a small rubber gasket wasn’t installed between the plug and boat. Not an issue on a fibreglass boat but many aluminum boats were toast by the time the owners new what was going on. In Lunds for example, they love to have electrolysis under the decals for some reason. I’ve seen several that were like tinfoil in places and the only thing that gave it away was the sticker bubbling. Don’t know why there, you would think it would only be in the bottom of the boat where there was some water for the current to react with.

[Wes_G]

Can you check if MAYBE someone has attached a ground cable from the battery to the aluminum hull somewhere? People do this sort of wiring on vehicles, but they do not understand that the wiring on a boat only grounds to the battery, and never to the aluminum hull.

Drewski

My first thought was that a ground is attached to the boat somewhere. But I know there is a green ground wire that does return to the negative side of the starting battery. I did buy this boat new so maybe when it was all rigged up at the dealer something got done wrong, that is kind of where I am at right now. I am no electrical expert though, so not %100 sure what it is I am looking at most of the time and likely wouldn't know just by looking at it if it was wired right or wrong.

[Sea Hawk]

Does the stray voltage disappear if you totally disconnect the battery.

[Tfng]

.

[Wes_G]

Does the stray voltage disappear if you totally disconnect the battery.

The stray current disappears once you disconnect both positive and negative. If you only disconnect one, it is still there.

[SamSteele]

My first thought was something is grounding out to the hull, causing the issue. You mentioned disconnecting the battery stops the voltage measurement at the hull. I would try disconnecting individual accessories to narrow down what wiring/item may be grounded incorrectly. If your boat has a fuse box that may be a good place to start. Pull a fuse and measure as you have been. Hopefully that narrows it down.


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[Dark]

My bilge pump does not go through the master switch, you might want to check to see if it's grounded properly.
My stereo was grounding through my aluminum dash I had to install my stereo in a plastic sleeve.

[EZM]

The stray current disappears once you disconnect both positive and negative. If you only disconnect one, it is still there.

A little late to discussion here - but agree with a few guys here - sounds like you are grounded to hull somewhere. That should NOT be the case.

I installed a blue sea fuse/electrical block, and had everything re-grounded and my issue disappeared.

There was some here on forum who gave some good advice as well ..... I believe it was a thread on the "black box" ... I went back and searched but couldn't find anything.

I'd start there, trace the ground and see what's happening there first.

[Wes_G]

My first thought was something is grounding out to the hull, causing the issue. You mentioned disconnecting the battery stops the voltage measurement at the hull. I would try disconnecting individual accessories to narrow down what wiring/item may be grounded incorrectly. If your boat has a fuse box that may be a good place to start. Pull a fuse and measure as you have been. Hopefully that narrows it down.


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I have had everything disconnected except for the main motor, but was still getting a reading so other than the main, I am not sure what else it could be. You would think that would be wired/grounded correctly though.

[Sea Hawk]

You may want to try running a ground wire from someplace on your engine(maybe a mounting bolt) to the negative post on your battery.

[Wes_G]

You may want to try running a ground wire from someplace on your engine(maybe a mounting bolt) to the negative post on your battery.

This intrigues me, It's about the only thing I haven't tried yet!!!

[Coiloil37]

You need to start by looking at how a boat is meant to be wired per ABYC and other regulatory bodies/ best practices. Then you need to see where your wiring job went wrong. My guess is that you’ve got a voltage leak. It might be as simple as where the battery isolator is touching the alloy of the boat. There is a ton of information on the web but this should get you started.

https://newboatbuilders.com/pages/elect.html


I rewired my boat last year although it’s glass so I didn’t have some of the issues you will. That said I run in the salt so I have many other issues you don’t. I did a ton of reading, talked to some sparkies and fixed all of my wiring up with blueseas components (isolators,busses,fuse blocks) and tinned marine wire.

If you don’t understand the basics and don’t put some photos up I’m not sure where to start trying to help you. Do some reading then ask some more relevant, specific questions or put some photos up.


Some good reading in here too but might be for boats a little more complex then what yours sounds like.

https://www.bristol27.com/projects/bonding-grounding-system

[Drewski Canuck]

DO you have an internal fuel tank, and if so, is it at the back of the boat, and if so is the fuel sender wiring ever submerged? The voltage goes the shortest distance to the electrolysis area so the source is likely stray voltage off something that is regularly powered like the fuel sender. Fuel sender wires are often bare connected, and there is ample water and moisture off a fuel tank to complete the path to the hull.

Drewski

[Wes_G]

DO you have an internal fuel tank, and if so, is it at the back of the boat, and if so is the fuel sender wiring ever submerged? The voltage goes the shortest distance to the electrolysis area so the source is likely stray voltage off something that is regularly powered like the fuel sender. Fuel sender wires are often bare connected, and there is ample water and moisture off a fuel tank to complete the path to the hull.

Drewski

No internal fuel tank.