If you have growth on the bottom, I would recommend Mary Kate's On/Off hull cleaner. Starbrite's hull cleaner isn't bad either. Both are acids, and you MUST read the directions & follow them. And, yes, of course, then you will need to wax the hull.<br />I too have used the 3M Restorer & wax. It will remove small dirt from say the top deck, but on the bottom of the hull, no, it can't remove that. I have also noticed that with the restorer, you need to use a second wax after that, in order to get a glossy shine. Something like 3M's Finesse It.Originally posted by Jack L:<br /> Any good ideas on how to clean the dirt off the bottom?<br /><br />I have used the 3M restorer & wax but it does not seem to clean it up. Suspect I need something stronger to get it clean, then wax it good.