Which gelcoat cleaners are best at combating waterline yellowing on boat hulls? Ben Meakins dons his rubber gloves and puts 10 products to the test
Grunt! Boat Cleaner contains no oxalic or hydrochloric acid, instead containing phosphoric acid (also found in Coca-Cola), and is thus said to be biodegradable and safer to use. It is painted on and left for 30-60 minutes before being washed off. This had to be left on for the longest time of the products tested, but upon rinsing off left the hull as clean as
the top tier of products save for the heaviest staining. However, as we tried this one at the bow where the staining was worst, that was to be expected. A second application saw to the remaining stains.