Transom corrosion / Electrolysis problem help

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80thdiv313fa
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Transom corrosion / Electrolysis problem help

#1

Post by 80thdiv313fa »

Hey guys I've got a problem I'm looking to get some advice on. I just can't get a straight answer from the dealer or manufacturer.

I own an 18' aluminum V hull boat. The boat is a 2007 model with a 90hp Yamaha engine on it. It has 3 batteries (2 connected to an onboard charger for a trolling motor) (1 for the engine and other electronics)

The transom is riveted and not fully welded. The splash well drains were rusted through to the point I can see the transom wood. There are 2 spots of corrosion in the transom that I could see straight through to the transom wood. I have since sealed these holes with JB Weld cause thats the only thing I could think of to do.

I'm not first owner so the manufacturer made it clear the warranty is void.

The dealer claims that it's chemicals in the transom wood causing a reaction with the aluminum.

The manufacturer claims that it's a grounding issue caused by faulty wiring by the dealer.

I put the negative lead of my volt meter on the battery. I put the positive lead on the transom and I get a very small amount of current. I don't see where any wires are connected to aluminum. How can I tell where the ground is at?

I really don't want this to progress. I can't see how this could be an issue in a 10 year old boat.
80thdiv313fa
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Re: Transom corrosion / Electrolysis problem help

#2

Post by 80thdiv313fa »

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80thdiv313fa
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Joined: Tue Mar 14, 2017 9:21 pm
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Re: Transom corrosion / Electrolysis problem help

#3

Post by 80thdiv313fa »

Just a little more info. I disconnected and took the batteries out for the winter. If you notice in the second picture these are 2 new corrosion spots on the transom inside.
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Re: Transom corrosion / Electrolysis problem help

#4

Post by welder »

If the manufacture use TREATED lumber in the transom you will have a problem.
Some that have had that problem ended up cutting the transom out/off and replacing it with thicker aluminum and no wood.

Others will be along to give more input on the subject.
Lester,
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Re: Transom corrosion / Electrolysis problem help

#5

Post by welder »

Here is a SeaArk transom repair....
viewtopic.php?f=13&t=1977&st=0&sk=t&sd=a
Lester,
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kmorin
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Re: Transom corrosion / Electrolysis problem help

#6

Post by kmorin »

'13fa, I'm not remarking about your electrical system or wiring, since we'd need to see a diagram and extensive photos to be informed enough to remark? I will summarize all DC electrical systems by saying they should be 'bonded' to the hull in one location and that is a single connection to the DC neg bus or battery terminal.

Generally, all DC related corrosion will happen in immersed portions of the hull- inside or outside - but wetted by bilge or water in which you're floating- so if you pulled your DC energy source out (? from your post) and subsequently had new corrosion sites emerge??? It's pretty safe bet you have a corrosion cell (or cells) working from one of the other two forms of corrosion (not stray current- leaves only galvanic or ph/crevice corrosion)

If the boat has a wood 'core' or insert inside the transom (?) then that is most likely the cause; OR, as Jamie and Adam used to say on MythBusters "There's your problem".

If you'd take a minute to search for and read our many threads on various corrosion types and what to do about them (?) then you'll be able to see why I assume that wetted wood, which has no provision to dry out, is the source of your problem. Unfortunately, you have purchased a "disposable" boat made by a company who was not concerned with longevity of their products - only initial sale. These disposable boats are well known to corrode at the transoms and there are well discussed corrections posted online.

We (AAB.com Forum) are more or less focused on (heavier) plate boats, or 'all welded' boats, so, while we also see our share of the three primary causes of aluminum corrosion I'm not sure there are many wood composite transom replacement threads here? (could be we've seen some in the past?) Welder linked to a few year old 'patch job' where the original problem looks like it was more or less - left in place? That is one way to 'fix' (?) the problem underlying the photos you show but that post essentially just covered over their real problem instead of removing the problem to actually cure the underlying designed corrosion cell(s).

I think there are number of riveted boat focused sites that have complete threads on transom replacements? I'm familiar with one fabrication shop in Georgia http://www.fishonfabrications.com/custo ... ation.html who have done complete transom jobs in riveted and thinner metal boats. I believe the owner has some posts (not sure where) showing this type of all metal replacement in at least one boat- perhaps there are more? Can't hurt to see if he can provide links if you can't find them with an online search?

Wet wood, that cannot dry, sandwiched by aluminum sheet is not sound boat design, however, it is inexpensive and allows boat's of this cost class to hold an outboard for many years of of service life, before the corrosive cell shows through the poorly designed construction.

Hope you're able to decide on a fix, I do encourage you to read more on the Forum's threads on corrosion to help increase your awareness of the performance of aluminum alloys as used in boats in different details. (I'd suggest you) Don't hesitate to PM the various posters on other sites who may have had similar problems and add their experiences/solutions to your knowledge as you plan to address this problem.

cheers,
Kevin Morin
Kenai, AK
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80thdiv313fa
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Re: Transom corrosion / Electrolysis problem help

#7

Post by 80thdiv313fa »

Thanks for the advice guys I really appreciate it.
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