gelcoat cleaning?

[westerner]

My friend has a boat that has rust and years of discoloration on the fiberglass hull and regular marine cleaners don't do much. The Glasply seems to have a good coating of gelcoat on it judging from a few misc chips so I'm thinking sanding could be an option. I believe we have had a discussion in the past on this at one time or another (may have been fiberglassics) but I couldn't find anything on it looking back.
In any event I think we have our work cut out for us. Any advice or reccomendations would be appreciated.

[Tim_Mattson]

Kent ,
It is a big job but it can be wetsanded to reveal that glorious color.Find a place where it won`t be hard to blend if you back out ,but trying a square and doing a test to see what lies beneath is always a good idea.
I`d start as fine as possible say 1000 or 800.Finer if you can but usually takes days no matter what.I`ve gone as low as 320 grit but only if never been buffed and gelcoat beneath is thick enough.
A little dishsoap will keep the sandpaper from grabbing,a small sponge and a bucket of clear rinse water will keep the color from staining the ground and piling up residue as you remove it.
Once getting it all uniform,you`ll need to wax it up to keep the surface beading up water and for dirt to be easily wiped away.
Rubbing compound and a power buffer can do the job much quicker but can devastate trim if caught in the spinning wool bonnet.
"Ospho" is what the yachts spray on the rusty stains,works awesome and is at hardware stores in crystal you mix with water.
Hopefully you get more advice from other`s ,I`m sure there is more to give.
TimM

[Helmar]

I myself have used the buffer with the 3M cutting agent, then polish.
I find that some of the salt water can really make some nasty stains as well.

Like Tim says, watch the buffer around trim as you can rip it right off if not real careful.

Anyone else

[westerner]

Tim and Joe, thanks so much for the expert advice. Will start on it shortly and let you know how it turned out. Just removing the rust would be a great improvement. Will probably try the hand sanding method first and end up with the buffer would be my guess.
Happy Fathers day guys!