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Originally posted by islander

Life seal is the go to for bedding plastics to fiberglass and is what I used when I replaced my dead light. Without knowing what sealant was used on your boat I can't recommend a product because they might not be compatible. Slapping one type of sealant on top of another that might or might not be compatible with each other could make things worse.

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Originally posted by Lee Panza

Any caulking material applied externally will eventually degrade in UV exposure. LifeSeal is supposed to be pretty good, but you can't expect it to be permanent. When it's completely covered under a UV-blocking surface, like under the flanges of a piece of deck hardware, it can last a long time (slight degradation occurs at the edge exposed to the environment, but it progresses inward very slowly). But as a bead applied to the outer edge of a joint it has no protection from UV exposure, so it will break down and eventually have to be replaced. The only real issue is how long it'll last (and up there at Whiskeytown you might only get a few years, Lucky, if you're still watching this thread).

A more important issue is adhesion between the caulking material and the substrate. Both surfaces have to be seriously clean, and they should be free of soft oxidized gelcoat or any protective waxes. The surfaces on both sides of the joint should be scrubbed with a solvent (taking care to remove it from the joint line, so it doesn't attack the existing sealant or interfere with the new caulk), and a light sanding would be helpful, too. This is pretty anal-compulsive, I know, but a little extra time spent now could add years of enjoyment of the results.

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