So if you put gel coat over the boat it would protect and seal it but it would still have the oxidized color? Does a good marine paint offer the boat anymore protection?
I think what you've yet to uncover in your web search is that Gelcoat is polyester resin. So, also, is the resin mixed with the fiberglass fabric that makes up the hull of your boat. Gelcoat is formulated to be more water resistant and UV resistant and it's colored, but the basic chemical formula is the same polyester plastic as the underlying structural layers that make up the rest of the hull.
Like a car finish, properly maintained gelcoat has a high-gloss and is highly resistant to environmental elements. Also like a car finish, when neglected it oxidizes to become dull, chalky and sun bleached. Proper maintenance involves an annual treatment with a formula that replaces the leeched out plasticizing chemicals and adds back a UV protecting layer. With cars we call the leeching out process, "that new car smell". The special chemical treatment we call, "waxing". Boats need the same care to last and look good.
Fiberglass boats are built in a mold from the outside in. They begin by laying down a layer of gelcoat, after the gelcoat has partially cured they begin layering in the structural fiber reinforced resin coats. When the process is finished all the layers have chemically linked to become one solid piece.
http://www.sunfishforum.com/content.php?pg=construction
The gelcoat layer of a fiberglass boat is right at about 0.02" thick. Paint layers are typically about 0.002" thick and two is the average..., or 0.004" total thickness. Both polyester gelcoat and marine formula polyurethane paint are about the same hardness and stand up to the elements about the same when cared for properly. Gelcoat has an advantage of being thicker so it can be abrasively rubbed out and polished up (not to be confused with maintenance waxing) more times before it needs to be recoated.
Properly maintained gelcoat on a "dry stored boat" rarely, if ever needs rubbing out so it lasts an incredibly long time. We are coming up on half a century for Sunfish and there are some beautiful boats out there with the original finish still gleeming.
Gelcoat is expensive to have re-applied so painting is usually the choice when the gelcoat has been rubbed off or neglected so badly it needs to be sanded away and replaced for looks and weather protection**.
**Maintaining the protection depends entirely on your degree of upkeep..., just like your car's paint job.
