Tri-Sodium Phosphate is the active ingredient in Spic n' Span and I've used it repeatedly on Ciao Bella with great results and no damage to gel coat. Remember to rinse thoroughly. For removal of black marks and heavy duty filth on the decks, I use a product designed to clean "cool-decking" which is an apron around swimming pools. "Klean-Deck" manfactured by SunCoast is available in your local pool supply store and is easy as pie. Mix according to directions, apply with a deck brush, wait 5 minutes and hose down and voila! Spotless decks! As far as the bilge is concerned, only cleaned it once and used Simple Green with great results.Neil SmithCiao Bella