I was curious also as to what polyurethane you used. When I was considering a varnish to use, very few on the board recommended that I use polyurethane because it was cloudy, brittle to a mention couple of things. I did a lot or searching for answers, even talking to the manufacture and buying a book on varnishes. I took a chance and settled on MinWax’s Helmsman Clear Polyurethane ( not the water soluble kind) because it was available everywhere locally, cheap, I got a quart on sale for less then $5 and dries in 4 hours. The quart finished my whole boat with 7 coats and was just the opposite of brittle in that it’s very flexible. I have never see any boat finished with the varnish most used on the board (seems to be Captains) so I can’t really compare, but I don’t see how it could be much more clear then what I used. I will use this product on my next boat.

I would think a chemical stripper would do a good job for you and not hurt the epoxy but I would try a small part on the boat just to be sure.

John