Removing Intracoastal Stain
While traveling up and down the Intracoastal Waterway, my boat ended up with a permanent brown stain around the bow and along the waterline.
I believe the stain is caused primarily by the presence of tannin in the water, which comes from trees and vegetation along the waterway, and possibly from high concentrations of iron in the water in some areas.
I found the best product for removing the brown stain is oxalic acid. You can find oxalic acid as an ingredient in some hull and fiberglass stain removers, which do a good job of removing the stain. But when doing a large hull, you will need a lot of product, which would soon become quite expensive. I have found it much more economical to buy the acid straight. You should use about 1 tablespoon per one-half bucket of water.
Using rubber gloves, apply with a large sponge and allow it to work for 5 or 10 minutes, then rinse well.
A protective layer of wax on the hull afterward would be a good idea.
- Steve Hicks