I'd like to patch over an old below the water line through-hull. Actually, I rather not, but I've been advised that the insurance company might expect me to. I'm not sure why a capped off through-hull is unsafe but once you stick a seacock and hose on it, clearly adding more points of failure while removing none, it's ok.
I was planning to use system 3 epoxy and 1708 (too heavy?) biaxial cloth with mat. I was also planning on doing the patching from the inside since I have easy access and there will be a lot less fairing and painting to do that way. Also easier to keep the glass in place with gravity working for me instead of against me. It's a small through-hull, probably 1". On the outside I was planning to fill with epoxy thickened with phenolic microballons (e.g. west 407) and then fair.
What, if anything, do I put on after fairing and before bottom paint? I was planning on using gel coat, but I've since found that polyester gel coat does not adhere to epoxy very well. Should I just use nothing before the bottom paint? Or just paint on some unthicked epoxy over the faired epoxy?