I had good results from Barkeepers Friend, which contains oxallic acid. It
wasn't so strong that I had to wear gloves. I sprinlked it on a dap rag,
wiped the surface and then washed it off with a wet rag. No scrubbing was
necessary. Bought it for less than $5 at Wal-Mart. Comes in a cardboard
cylinder shaped container like kitchen cleansers. I think it was in the
section with all of the household cleaners in the grocery section.
"Wayne.B" wrote in message
...
On Sun, 12 Mar 2006 15:24:57 -0600, (Gudmundur)
wrote:

Hi Folks,

I have just a small 15ft fiberglass open bow ski boat. I am it's
second owner, and the first owner left it in the river about 8 months
every year. Problem is he never cleaned the scum and grime from the
underside. The whole bottom of the boat now feels like 80 grit sandpaper.

I realize cleaning this mess up won't be easy, but can anyone recommend
a good cleaner to help remove the scale? I thought the fiberglass was
actually damaged but that does not seem to be the case. My trailer has
bunks without rollers and I have found that the areas that slid on the
bunks are scale free, this includes the recent areas where I hit the bunks
a little off to the side.

As scaled up as the bottom is it would seem I may be losing a few MPH
on the top end. It will be interesting to do a before/after speed check.

West Marine sells a product called "On and Off" which is a powerful
acid based formulation that is as close to a miracle cleaner as
anything I've ever seen. Read the directions carefully, wear rubber
gloves and eye protection.