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The absolute last thing you should do with gelcoat is to paint it. There is NO boat paint on this planet that will withstand the rigors of a 'boating environment' as well as simple gelcoat.
Gelcoat is usually quite thick, in most cases easily restored back to 'showroom conditions' ... and even if your restoration so 'thins' by agressive sanding/polishing the gel, you can easily spray new (and colormatched) gel over the old.
First get a pocket low power microscope and look at the condition of the gelcoat. When look at the gel under the microscope ... what you dont want to see is something that looks like a dried out pond .... little cracks looking like the back of an alligator. If thats the case, the gel is gone over the the darkside and cant be buffed/sanded and must be entirely removed and gel resprayed .... in this case you apply a barrier epoxy primer and then and PAINT the boat. If the gel under the microscope looks reasonably intact (no microcracks) then you can sand away with extremely fine wet/dry paper (600 ---> 1000 ----> 1300 ----> 2000 grit) over a rubber sanding block until you have a FLAT surface. Keep the paper wet when sanding and use a few drops of dishwashing detergent to 'lubricate' the paper and to keep it from clogging with removed gel. You can add gelcoat patch to the gouges, large cracks, etc. before sanding down; you can have the repair gelcoat computer matched to the exact color of your hull topsides, etc. .... just do a websearch for the suppliers and methods.
Once carefully flat-sanded down, then use a variable high speed autobodyshop polisher and 'knobby foam rubber' polishing bonnets. If you sanded as above you can 'start' buffing-out with 3M Finese-it (about 1300 grit compound) .... Buff out in 2ft. by 2ft. squares until you complete the whole boat surface to be buffed. Keep the buffing pad 'moving' across the surface so you dont burn the gel; be escpecially careful around edges and corners as they rapidily can be buffed through to the FGR matting layer.
Repeat the buffing on the areas that dont return to a 'decent' shine.
Then repeat the buffing-out using a new knobby foam rubber polishing pad and 3M "Perfect-it" polishing compound (probably @ 2000-3000 grit). At this point in the restoration process the surface should look like the day that the boat was in the showroom.
Finish by waxing the surface ..... but in a special way to insure that wax get INTO the pores of the gel and so that it doesnt begin to oxidize all over again. WET your BARE hand, rub on some natural Brazilian CARNAUBA (Collenite Fleetwax, etc.) and PUSH the wax into the surface, keep rubbing and pushing until the wax disappears and the 2x2 area gleams, then wax again using a very small amount of wax until the surface gleams, apply a 'dime size' amount of wax to you hand and smear it all over the 2x2, let partly dry and then BUFF with a clean knobby pad at moderately high speed.
Continue in 2x2ft. squares until the boat 'dazzles' like it did when it was band new.
Finalize (remove wax streakes, etc.) using a wet bare hand, a teeny bit of wax .... and wipe it clean with a MICROFIBER polishing cloth.
BTW this is the way a boat is buffed-out when its pulled from its mold !!!!!!
If you have small areas that after buffing that have become 'thin' and you can see the color/patterns of underlayment throgh the gel, then do websearch for "gelcoat spraying" + repair. You can buy selfcontained spray bottles (PreVal Spray bottles) with which to spray on the gel and the 'finishing chemicals that are sprayed on top of the fresh gel, etc.)
Dont paint your bout unless its absolutely necessary. Its easy (but a time consuming job) to restore just about any gelcoat back to the original shine. Original gelcoat is quite thick ... up to 3/32" thick .... dont be afraid to buff out gelcoat. Even if you burn-through or sand too deep, gelcoat repair is fairly easy (if you arent a klutz).
Id also avoid the "acrylic coatings" such as "Island Girl", etc. as they ultimately need to be entirely removed and if you dont your boat will look like it has a skin disease until you do remove it.
Last edited by RichH; 10-02-2009 at 05:54 PM.