As most owners of fiberglass boats will tell you, cleaning fiberglass boat hulls requires different cleaning methods and materials than cleaning the hulls of boats made of wood or metal. Why? Because the color and sheen created by the gel coat finish of a fiberglass boat can easily be damaged if treated harshly. Cleaning of these boat hulls requires different methods and cleaners, depending on stains you are removing.
Dirt and Salt
Tiny dirt and salt particles can be abrasive and can dull the shine of a fiberglass boat hull and can heighten damage from the sun's UV rays if they are not cleaned off using proper techniques. To avoid this damage, clean with a soap specially manufactured for cleaning fiberglass boats, scrubbing gently with a soft bristle brush.
Some bodies of water can leave brownish stains at the waterline of boats traversing these waterways. Cleaning products that contain acids are especially effective in removing these stains.
To remove rust stains from the boat hull's gel coat, as well as painted and metal surfaces, apply a special hull cleaning product. Allow the cleaner to sit for several minutes, then flush it off with water. For hard-to-remove rust stains, scrub with a soft bristle brush after applying the cleaner. Always apply a new coat of wax, afterward.