Originally Posted by Rossterman
Did the 100% vinegar test and not much improvement
guess I'll need to consider some polishing or rubbing compound...
Any time something is on a surface and it doesn't come off by wiping, you need to find out what the substance's base is- water, acid or oil. If it doesn't come off using water, use vinegar. try denatured alcohol, then mineral spirits. If that doesn't work, use Oops or Goof-Off. You always want to use the mildest solvent on gel coat because it's porous and if you use a really aggressive solvent, the staining can become permanent.
If the hull was waxed before you went, it's likely that these spots are oil or ammonia-based and those will remove wax. Ammonia is one of the by-products of decaying animals and vegetation and WRT Ph level, it's somewhat basic, while waxes and oils are acidic and a solvent with the opposite range of Ph will dissolve it (acids and bases neutralize each other). If an acid won't remove the stains, try a solution of baking soda and water.