gripit

Whats a good product to clean a smooth gel coat deck? The deck has deep dirt and grime buildup that actually makes portions of it a little yellow. Also, when looking at it very close, I can see little black speckles all over the deck the size of pin holes. The boat is an 1988 and has been poorly cared for but the deck doesn't have any oxidation. Only deep dirt. I was thinking of on-off but didn't know if that would be to strong. Any suggestions will be appreciated.