It takes a ton of work to bring back the gel coat once faded, but it can be done.
My Edinboro was totally oxidized - so much so it looked like a "pink" boat, rather than red.
I did not do it myself (although I tried), but paid the restorer to bring it back. Took nine steps:
First four steps consisted of sand papering by hand, starting with 800, and moving through to ultra-fine (2000) for the fourth step. Good news is MFG deck gelcoats used back then were very, very thick, and this can be done without exposing the glass cloth underneath. Hull gel coats are a different story, as the hulls are made with a chopped glass and resin composite, molded and cured under heat and pressure with matched metals dies - unique to those lapstrake-style MFGs. I would only do this on a lapstrake MFG. The gelcoats on the tri-hull (Gypsy) and deep-v (Caprice) boats were much thinner and the fiberglass cloth shows more easily after sanding.
Then, four steps of high-speed polishing, using Presta boat polishes of lighter and lighter cutting capabilities. (See
www.prestaproducts.com/Buffing_Compounds-list.aspx
: )
Last step was with a UV glaze to help protect the surface (pick one - there are several out there). When done, it was then back to close to original shine. However, it's critical to protect this "new" finish.
No easy solution. While I tried to do it myself, it was going to take a whole summer and lots of hours, and I decided to pay to have it done. Expensive, but in the overall cost for a restoration, not bad. That said, from an economic standpoint, it is much better to find a real good one in original and unrestored state. Good restorations are expensive, and I insisted on gel coat repairs and not paint. That made it even more expensive. My Niagara is original and unrestored, with a shiny blue gel coat. Note: you'll never get the money back from a restoration. In my case, "Big Red" is the only red Edinboro I ever found in looking for two years that came with those red and white Sun 'n Fun seats. It was worth it to me to do it, but only to that particular boat, for me anyway. It will be the only boat restoration I will ever do.
Pay close attention to your transom. They tend to rot out. My Niagara is original, while the Edinboro has a poured repaired/replacement transom using Carbon-Core CarbonBond.