cleaning vinyl

Been cleaning the vinyl on my recently purchased boat. Lots of good tips here. Tried some Maguiars (sp?) vinyl cleaner and magic erasers. The magic erasers seem to work great and I picked up some 303 protectant. Is there anything that will take of the yellowish stains on the seats where the cushions but up against the backrests. It's stained yellowish and with some brown spots. The magic eraser helped, but didn't remove it completely. Is it there to stay or is there something else to try? I did read a post made a while back about Star brite mold and mildew cleaner and was thinking of ordering that but could only find it in a spray formula, not a chalky liquid like the poster stated and had pictured in the thread?