When your boat’s hull is stained or dirty beyond the power of most fiberglass cleaners, use MaryKate On & Off Gel for the toughest job. This is a serious acidic chemical that is safe on fiberglass, as long as you follow the precautions.
Use is simple: just brush it on, let it work for a few minutes, and hose it off. Be sure to wear heavy waterproof gloves, eye protection, and a respiratory mask.
Take a look at the before-and-after photos on the next pages.