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Join Date: Sep 2005
Location: New Westminster, BC
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For ultimate satisfaction, it sounds like you'd better be resigned to removing the old paint, properly prepping the hull and respraying with a good 2part Polyurethane or epoxy primers and paint. Such a job, done properly will out-last, out-look, and out-perform an after-the-fact gel coat job.
What you are describing sounds like a bit of a botched DIY job, so putting anything on top is risky. Get down to the bare glass, consult your supplier of choice and use all the proper materials, primers, reducers, as recommended.
Doing anything else will risk losing the considerable investment of time and money on the project.
To be considering purchasing a boat in that condition should mean a substantial price reduction over the average for that model of boat.
Be sure you're prepared to take on a project like that. These days it usually means finding an enclosed place to work, few yards will let you sand and spray anymore. The costs of rentals, storage, lift and transport fees should be factored into your equation as well.