John H. wrote:
On Sun, 28 Oct 2007 14:39:12 GMT, "Canuck57"
wrote:

"Gene Kearns" wrote in message
...
On Sun, 28 Oct 2007 00:44:21 -0500, sherwindu penned the following
well considered thoughts to the readers of rec.boats:

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
We have the same problem here in the rivers and the AICW.... I have
constantly fought this battle and won.

First of all, I would caution against using any powdered cleaners.
They are all abrasive, to some extent, and I suspect do more harm than
good.

Gelcoat is porous. Sorry, but that is just the way it is. Your cleaner
is going to have to go where the stain is and chemically remove it.
The only way to actually do this is acid.... and it might be
hydrochloric (muriatic), oxalic, phosphoric, oxalic, sulfuric or a
mixture, including detergents or surfactants. Read that, "I gotta wear
eye and skin protection!" Thus, also, you have the reason the toilet
bowl cleaners can be used.... they are acid. They can be bought
cheaper that the boutique cleaner blends offered in most chandleries.

This is one easily obtainable boat product with which I have had good
results:
http://tinyurl.com/24gcep

NOTICE: that any acid based cleaner is NOT good for your trailer.....
especially if it is aluminum. It will stain and etch the metal.

ALSO NOTICE: (at least in my experience) any acid cleaner is going to
screw up your bottom paint. I use a black ablative paint and it
doesn't really stain, so I use tape and plastic to mask off my bottom
paint. If your paint cannot be washed clean.... I think you are in for
scrubbing and a touch-up.

What about waxing it before going out? Any thoughts on this? Is there a
easy treatment that makes it come off easy?

I know it doesn't get it off once on, but maybe an ounce of prevention is
better than the cure.


You can buy oxalic acid powder at hardware stores. $5 will get about a half
pound which will make enough solution for several years. I use about two
tablespoons per gallon of water, put it in a spray bottle, mist it on the
brown stain, wipe with a sponge, and then rinse. The stain is gone.

This is much cheaper than Off and On, it is worth a try, even if I lose
the rest before i need to use it again. Maybe we can just buy a half
pound for the whole dock.