Cleaning of stains...Please Help

I had my boat in my yeard and looked in side of it one day to find sh*t loads of those little "helicopter" thingies that fell out of a tree. They have left stains from when they got wet from condensation and I have tried 3 different cleaners and two different brushes to try to remove these stains. Does anybody or has anybody had this happen or know how to get rid of them? Thanks in advance. -Burn