Best way?....new seats or re-upholster. You can see similar damage I had in the pic. I went as long as I could.
You can possible stretch a few years using a majic eraser, and vinyl cleaners. I also used a small sponge with some clorox in it on just those areas. It helped but eventually it hits a point of no return.
The issue, as in my case, was caused by the cover pressing against the vinyl under summer sun. The heat gets concentrated and bakes the vinyl over periods of years. Mine did last 17 years, not too bad.
My hopeful cure is my new, white cover with extra padding sewn in where the cover touches the seat backs and sundeck. It's a catch 22 unless your boat is in a covered slip.
Some have said it can be painted with a vinyl paint.
