Ever since the government ruined the paint stripping products, this has become my "go to" paint stripper. It will not harm gel coat. Pricey though....
https://www.totalboat.com/product/total-paint-stripper
They also have fiberglas repair products....
https://www.totalboat.com/product-ca...ategory_id=236
https://www.totalboat.com/product-category/resins/