[Gerry Zagorski]

Dawn is a great cleaner and cheap and that's what a lot of people use. Not sure it's meant to be used in the marine environment though.

Best boat soap I've found is Crazy Clean. Comes in concentrate and a few squirts on the deck is all you need. Cleans like no other soap I've ever used.

Any soap that is farily aggressive on stains is going to take some wax off.
Best thing to do is occationally treat your high traffic areas like the deck with Woody Wax so the decks won't stain as easily to begin with. Once the deck is clean, you spray it on wait for a few minutes and hose it off. Great for non skid since it's not slippery once hosed off. It is however expensive.

Hope this helps.