Our best guess is that a previous owner of our boat was a smoker. Thankfully no smells related to that, but the vinyl headliner has light brown stains in some places, leaving a somewhat mottled appearance. I've tried pretty much everything that I can think of from mild to downright nasty to try to get them to go away. In some areas the staining has lessened, but never goes away.
Anyone used vinyl paint to freshen it up?