After pulling my boat from the Root River in Racine Wisconsin, I noticed that
there
was an ugly band of black gunk at the waterline, especially at the upstream side
of
the boat when it was in the slip. A power wash got the mud off, but this band
of
gunk stayed on. I had the same problem last year, and had to rub like hell with

all kinds of cleaners to get it off. Someone recommended using Tidy Bowl as a
cleaner, possibly because it contains Muratic Acid. I know that Muratic Acid is

used to clean and etch concrete, so I was wary to use it on my fiberglass hull.
Was I correct about this? Is there a better way to clean off this river junk?
I
have used Zud and other similar products, but they don't get everything off and
require a lot of elbow grease. Some of this gunk is on the bottom paint, as
well,
so I have to be careful not to dissolve that.

Sherwin