How Do You Remove Diesel Exhaust Stains From Gelcoat?

When a boat builder lays up a fiberglass hull, a mold release agent is sprayed into the boat mold, then a thin layer of Gel Coat is sprayed over the mold, followed by fiberglass, a core and more fiberglass. That thin Gel Coat -- the first layer applied -- stays on the fiberglass and provides all the color and gloss. If diesel exhaust stains develop on the surface of the Gel Coat, the right cleaner takes them off. If the stain goes deeper, a bit of elbow grease and a product from the automotive world can help. Apply the fiberglass stain remover to the stained area with a clean rag. The stain is the result of soot being deposited on your hull. Soot is the gray-black "smoke" that comes from all diesel engines. Wet exhaust systems mix the exhaust gases with seawater and discharge those gases from ports on the side of the hull. Dry exhaust systems discharge the soot directly into the atmosphere and, inevitably, some stays with your boat. Wait 10 minutes. If the stain is simply laying on ...  more