so I uncovered the boat today and there was what looked like urine on the transom hatch. (not sure what it was though) there were no stains on the cover, nor was it wet. Tried cleaning it with simple green, heavy duty vinyl cleaner, a sponge and comet, and a magic eraser (all at different times) nothing worked as a stain is still there. Any suggestions???? I know this has been discussed before, but people always have good ideas here.