I have read it depends on if you wash it in or out of the water and of course how dirty/contaminated the boat is. If out of the water and in pretty good shape most any car wash product will do. Heck, I have even used ONR before. If it will be cleaned while still in the water a Marine product is best because it suds up less and causes less foam etc in the water. If the boat is in pretty bad shape and something stronger than a marine/car shampoo type product is needed they make special hull cleaners. Zing hull is all that comes to my mind, and I have no opinion on that product because I have never used it. HTH