This Thread was covered last year. I'm bringing it back because Spring is when Artillery Fungus is active and few are know of this. Please refer to:
http://plantclinic.cornell.edu/FactS...leryfungus.htm
My boat is covered with these tiny, hard shelled, pinhead sized, black spots. When the shell is scraped off, inside is a black tarry substance that stains the fiberglass. So far nothing removes these stains easy. I have a stockpile of failed products like: MEK, accetone, paint thinner, bleach, Magic Eraser, rubbing compounds, On/Off Bottom Cleaner and a variety of stain removers and cleaners. I've had a Marine Surveyor and a Marine Finisher look at it and both say use 1000 grit wet/dry sandpaper sanding wet, followed by rubbing compound, polishing compound and wax. My boat is a 1990 that has seen several years of California and Maryland sunshine so the gelcoat is pretty much gone which dosen't help matters.
When they built my house in 2003, they cleared the lot of trees, hauled off the logs and chipped the branches into a huge pile in the woods. When I moved in, I backed my boat up on a flat area next to the woods near this pile. The decaying wood chips, oak and pine, and the spours from that decay is what Artillery Fungus is. It travels about 20 feet in the air and is attracted to the sunshine or a nice white boat. My 22 foot boat is covered from the roof to the keel, on everything, even the trailer.
Please keep your toys away from wood chips.