Transom Refinishing

[Aqualund1981]

I have refinished the transom on my GB42 but the finish did not last.
Appears to be getting moisture from underneath, finish did not pee but just turn white underneath.
Is there something I need to do to prevent moisture from getting between the fiberglass and the wood.

 

[Cigatoo]

On the Grand Banks the transom is the 1 place where there is any coring in the hull. It is limited to the space behind the teak. My believe is that they put coring between the 2 layers of glass in the transom is so the screws holding the teak planking had something to bite into. That coring has a reputation for getting water logged. If you can get down inside the lazarette look for evidence of brown goo or the like. It’s a good chance that is where your moisture is coming from.

Also there is an eyebrow (1/2 round I believe) molding along the top of the transom teak. Be sure that is is not letting water down behind it.

 

[BruceK]

This GB feature was copied into my IG, so watching for any advice on a fix. I suspected moisture wicking in on screws attaching name/port boards as a cause if care is not taken to use sealant when refitting them.

 

[Aqualund1981]

I suspected screw holes as well but the small white areas appears all over the transom.
Definitely moisture on the backside maybe getting between the planks.
Last time i completely stripped the transom, let it dry in the sun for about a week, applied a coat of thinned West system epoxy and then 6 coats of varnish. Looked perfect for one season and started to see small white spots under the entire system in the 2nd year.

 

[BruceK]

Your thorough refinish could be holding moisture in. Is there a varnish which allows moisture to escape through it? I know plastic paints do better in that regard with house walls subject to moisture, than oil paints. I`ve a memory Cetol varnish may claim that ability.
I toyed with cutting holes and fitting neat stainless steel vents to the inside of the transom, this would be allowing moisture to escape rather than preventing entry.
Another possible moisture entry point could be the feet and bolts of the stanchions supporting the cap rails across the transom.

 

[Westiculo]

Ah,
This happened to me before. I don't believe it's moisture. I completely encapsulated some name plates with west system epoxy then went over them with a two part varnish. The problem is amine blush. I tried to make sure there wasn't any on mine, but even a trace of it will cause your varnish to pop off. I have it happening in two specific areas of my name plates, not related to moisture.
How well did you scrub for blush?

 

[BruceK]

I thought this was a "snap"(shared) problem. While it has a similar result,the cause may be different.
To round off, someone painted my transom in 2 pack before my purchase(was the varnish bubbling?). It develops bubbles,and they contain liquid, ? water. Big task to take it back to teak after painting.
Now back to solving the OP`s question.