Bubble in transom paint

General boating discussion
Tedwin
Posts: 1
Joined: Wed Sep 08, 2021 7:11 am

Bubble in transom paint

#1

Post by Tedwin »

Hi, this is my first post and I'm glad to be here.

I have a 2006 LOWE FM165 that I bought about six years ago. Last fall I notice a small bubble under the paint on the transom. The bubble was completely filled with water and when I removed the paint there was a small pin whole in the aluminum. Fast forward to this year and I have three new bubbles. They all seem to be around the bow eye except for the one from last year which is a little lower. I removed the transom cap and the wood seems solid from what I can see.

The boat is kept out of water (freshwater) and is always covered. The only thing that I've done in the last year is add a on board battery charger for my trolling motor. I mention this because I installed the charger in August of 2020 and noticed the first bubble in late October.

Looking for some advice on what is causing this and suggestions on how to resolve it. Thanks

PXL_20210903_121809670.jpg
PXL_20210903_121809670.jpg (43 KiB) Viewed 230 times
Trousertrout
Posts: 43
Joined: Sat Jan 14, 2017 1:02 pm

Re: Bubble in transom paint

#2

Post by Trousertrout »

I would imagine that the thin aluminum is pitted on your transom. There should be a thick piece of marine grade wood behind the aluminum on the transom. The wood over a period of time wicks up the water and is slowly seeping out of the pinholes in the aluminum. What I have done in the past on lunds and StarCrafts is to cut a piece of 1/4"or 3/8" aluminum the exact dimensions of the transom and marine siliconed and bolted all the way through. You can also replaced the wood in the transom with new. You can also leave it alone and maybe get another 10years out of it until the transom gets too mushy. You will know this when you can actually see the transom warping during acceleration. Good luck
kmorin
Donator 08, 09, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21
Posts: 1640
Joined: Mon Aug 18, 2008 1:37 am
Location: Kenai, Alaska

Re: Bubble in transom paint

#3

Post by kmorin »

Ted,
the age of boat is plenty of time to get the transom 'board' saturated with water and therefore, a T'Trout suggests to pit from the inside out and bleed some water into a space under the paint film. By very close inspection of the pitting you're showing (magnifying glass 5X or greater) you will probably be able to tell if the pit is conic outside or not? If the pit is more or less cylindrical- that implies the corrosion cone is inside and T'trout's assertion is likely valid.

Inspecting the wood in the transom composite at the top isn't really going to tell much about that material's interaction with the thin aluminum cladding at the level of the bubbles/blisters/pin holes, you could also drill some holes (which you can patch with a bolt and some calk) and see if any water drips out? If the transom board is wet- then you have found your source of pitting (crevice corrosion from inside the 'sandwich' of the transom) and you might find means to improve the current status of a wetted transom 'core'.

If there is pitting at the bow? then look for any inside components that might contribute? Is the bow eye aluminum or another metal? Are there back up or 'doubler' materials inside the bow stem near or behind the bow eye? All these conditions would be important to know before trying to diagnose your problem in preparation for a remodel to cure/solve/remedy the design problems that caused your pitting and resulting paint blisters.

Cheers,
Kevin Morin
Keani, AK
kmorin
kmorin
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Joined: Mon Aug 18, 2008 1:37 am
Location: Kenai, Alaska

Re: Bubble in transom paint

#4

Post by kmorin »

Ted, something else occurred to me looking a the picture of the transom hold down and the bubbles/blisters in your a paint.

What if the area around those tie down transom penetrations were soaked? (not unreasonable to assume- even if they were sealed in calk) The cadimium plating or even SS or about any metal but zinc would have been subject to some pretty severe galvanic corrosion and that would likely be spread through a thin film of water- to the surrounding area - and then pin holes would be pretty common. This is just speculation but it does add to the probability that T'Trout's speculation is correct- the corrosion may well have come from inside the thin transom covering.

Cheers,
Kevin Morin
Kenai, AK
kmorin
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