On Sun, 28 Oct 2007 23:37:05 -0600, sherwindu
wrote:

Thanks for all the replies.

As far as wax, I give the hull a good coating of high quality boat wax before the
spring launch, and it doesn't seem to help protect the boat. This fresh water river

must have some nasty chemicals in it. I certainly wouldn't go in this water to try
and
clean the boat during the season. I have tried various products containing bleach,
oxalic acid, etc. and haven't found an effective cleaner yet. I am still wondering
if
using these acid products full strength might do damage to the fiberglass, so maybe
they should be diluted (how much?). If they use muriatic acid to etch concrete,
that
sounds scary. I will check out the 'on and off' product. I eventually got most of
the
stain off using a heavy duty liquid cleaner, but it took a lot of rubbing. I have
used
most of the commercial products mentioned in this thread, with not much luck.

Sherwin

I use an acid based cleaner from WalMart called, surprisingly enough,
Hull Cleaner that they sell in the boating/fishing section. I am sure
that it is just some basic acid that you can get cheaper in some other
form, but a quart container lasts me through at least 10 cleanings. I
boat in the Ohio River and if left in even over night there is a brown
to black stain that will not come off with any soap I have tried. With
this stuff I first wash with soap, then just sponge this stuff on
sparingly with a long handled cleaner with a cloth head. I spray some
around the outdrive and other hard to get too areas. Wait 10 seconds
or so and spray it off and the boat is white again. It doesn't matter
whether the boat was left in overnight or for 3 weeks, the stain comes
off just as quickly. I would bet that this stuff eats off the wax the
first time I use it and I only wax once a season. I have used it for
several years and see absolutely no impact on the fiberglass. I do NOT
have bottom paint on the boat, though.

Dave Hall