I have a 1984 Hunter 31 and for the last three years I have been having problems with mildew growing on the hull above the boot stripe. It will keep spreading if I don't remove it with a muratic acid and water solution. The wash lasts for about a month and the mildew comes back. There is another Hunter 31 on the dock and he has the same problem, but no other boats are affected, even boats that are older. I wax the hull every spring but it doesn't seem to help. The boat is kept in fresh water in Wisconsin. Does anyone know of a product that will stop this from happening?