I second Mag502num...Soft Scrub with or without bleach. Both work great!

I had a yellow, almost tarnish-looking coating on the transom that I couldn't get out with most cleaners or FSR. Tried Soft Scrub, a 'lil "wax on wax off" and turned out white as ever.

On another note, West Marine has a product called, Black Streak remover. Killer ****!
Had these bugs or spiders that oozed little black tar-like spots on my boat. Tried Soft Scrub, rubbing compound, FSR...thought I was going to have to live with it. Tried the Black Streak remover and took it right out.

...with my luck, it was probably a $12 bottle of bleach and water but it worked.

My '66 Shelby GT350 was midnight blue with white stripes and after a week of driving/racing the stripes at the rear were a light gray. Fantastic was the only product I could find that would clean it. It also took the wax off at the same time. I religiously washed and waxed it weekly.

I'd say try Fantastic and see what happens.