Cleaning Goo from Hull?

[viben]

An older fender has left an ugly, big stain on the hull over the winter, and I need some advice on how to safely remove it without damaging the gel coat.


The stain is "gooey", but quite firm, as a blackish layer on top of the gel coat. I have no idea what it could be.



I have tried regular cleaning products, scrubs and elbow grease, but to no avail. I have also tried Goo Gone, which did noting to dissolve it.


Someone suggested I try acetone. Another suggested paint brush cleaner. I worry that will damage the gel coat.


Suggestions?

[thinwater]

Xylene. Done it many times.

[S/V Illusion]

Xylene or hexane will remove the plasticizers which adhere to the topsides. Both safer than acetone but don’t use any of them if the topsides is painted. And obviously trash the fender (s) before this gets to be a habit