Electrolysis around engine sea water intakes

the paint could be flaking off due to poor surface preperation. Are the thru hulls bronze and if so are they displaying signs of corrosion or a pinkish color? If the answer to question 2 seems correct hire a amrine surveyor and have him test for stray current.

Is that intake electrically bonded?

What does the wood around the through hull look like inside the boat? Is it showing fuzzy fibers and/or white crystals? Does it appear swollen at all?

I would remove those throughulls, inspect the penetrations very closely, dry and treat the wood in that area with vinegar, and if in good shape, epoxy seal them then replace the throughhull without bonding. Apply the final coat of anti-fouling and look at them next haulout.

Marmot, I never heard of vinegar treatment what does that do? I know it is a preatreatment prior to painting galvanize but wood that's new. You learn something new every day.

Wood is subject to a form of electrolysis that creates sodium hydroxide, a strong alkaline chemical (lye - Drano) that dissolves the lignin that binds the wood fibers together and destroys the structure. When it gets really bad you can see white crystals all around the metal bits that appear to be sinking into a bundle of loose wood fibers.

Vinegar is acidic and it neutralizes the hydroxide and stops or at least seriously inhibits the process. If you have such a process going on, the vinegar (white apple cider vinegar - nothing fancy) will fizz and bubble when it soaks into the wood. If it doesn't fizz, you are OK and only stunk up the place for a bit.

Unbonding the throughull opens the circuit that is responsible for the electrochemical process that produces the hydroxide.

Go talk to some of the old timers at the wooden boat school in Newport, they can probably tell you some horror stories.

i grew up with the old timers and unfortunatly I am becoming one. I just never saw that solution. Like I said you never stop learning.

That I didn't know.