Oven cleaner
My folks just updated their boat name from paint to vinyl. It had withstood (sort of) the Mexican sun for 10 years and then the Oregon coast for another 5. Needless to say, the name was just a tad ratty. So, per advice here & elsewhere, I tried the oven cleaner method. While it did seem to work on the paint, it also turned the gelcoat an alarming yellow! Dad just about had a fit, so we wet sanded the rest off. Luckily the yellow faded away over the weekend but the wet sanding worked just as well, if not better since we would have had to sand to fair it out. We used 600 grit wet/dry sandpaper. Tried to find higher grit but the selection is limited in Astoria. Try the EZ Off first - any yellowing *should* fade away.

LaDonna