I see there are alot more sparkly boats around, I found this stuff works great and seems to make the crud come of easier
http://www.larsensales.com/ restore cleaner and polish
I usually give my boat a wipe down after i take it out, then spray this on lightly wipe it down to spread it evenly, let it sit for a minute then wipe down one more time for a shine
If you really want it clean when you have some extra off the water time use a clay bar and restore, smooooooth
http://www.web-cars.com/detail/clay.php