Sharkhide aluminum cleaner first. Then use sharkhide aluminum protectant to seal in the finish. If you have a thick water line you can apply muriatic acid to the waterline and almost watch it dissolve. Use the acid with caution and also get the waterline off before using the sharkhide aluminum cleaner. Check out my rebuild at here. I have a 1977 playcraft and the pontoons were nasty looking. I used the process above with great results. http://www.pontoonstuff.com/psforum/forum_posts.asp?TID=5719&title=mfwyatt-1977-playcraft-24ft-rebuild
