Rick, mine is significantly older 83. My gel coat was gone and I had to paint my entire topside. So, I have no experience with what you are trying to do. I have used a Mr. Clean Magic Eraser to great affect on my gel oat and paint. May want to take a wack at the stains with one of those or some bleach. I had what I thought were stains in the low spaces on my non-skid, turned out it was something biological and the bleach made it go away. Sorry I'm not more help, good luck!