Peeling topside enamel paint

Vessel: 48 year old 41' fiberglass sloop
Issue: Approximately 20 years ago a former owner painted the topside with a gloss black enamel (black over the original black).Looked great for around 15 years. I was not aware that it was enamel paint and for years I washed and waxed as you would for gelcoat. Around 5 years ago sections started to peel ( like badly sunburned skin peels). Looks like mostly the gloss coating is peeling as the underlying black is not peeling but is dull. Have tried compounding, but that doesn't seem to help. Given the boats age, I am not inclined to spring for a professional repaint. Vessel is based on L.I sound.Does anyone have any recommendations? Thanks.

 

From the wording of your post it sounds as though the 2nd coat of black paint is peeling loose from the original coat of black paint.
That might point to insufficient prep work on the original paint before putting the second paint on,, or some kind of in-compatibility between the two products.
Compounding is rarely the answer for any kind of paint product,, it gives temporary "relief", so to speak, but makes any kind of of a re-paint job a nightmare.
Once a surface has been compounded/buffed the only way to get subsequent paint to adhere is a seemingly endless amount of de-waxing/sanding/cleaning,, more sanding and solvents,, ad infinitum.
Perhaps some "pros" at painting will chime-in with a better "tech" solution.

 

For ordinary alkyd or one-pack Polyurethane enamel to last 15 years out in the weather, is a pretty good result, so I wouldn't be looking for flaws in what has been done, it just sounds like it reached the end of its life expectancy. The dull black might be gel coat, it could have weathered and that's why it was painted. It is a problem that you have been using polish, creating a surface contamination problem, but not insurmountable. I wonder what a high pressure water blaster might do, the cheap ones don't have enough pressure, but I have seen glass boats that had been painted over, just shed the paint in sheets, when hit with a water blaster at low angles. That was on a boat where it was peeling off, for who knows what reason, inadequate surface prep is commonplace with amateur painters, or it could be that the finish was incompatible with the substrate, that is unlikely in your case, as it looked good for years. It could be that yours just "gave up the ghost" with age. But a water blaster will tell you if adhesion is dodgy. Another way to check paint adhesion, scratch a cross like an "X" in the surface with a box cutter, apply and press on some Scotch tape, then rip it off, if the paint doesn't come away on the tape, adhesion is sound.

 

15 years for black alkyd enamel paint is exceptional.
Waxing and buffing didn't hurt it. Until it started to fail. Then continuing to compound add problems to the refinish.

It's time to remove the rest of it and start over.

I highly recommend changing the color. Black is difficult for pros to do well.

Single part urathane enamel should last a decade or two. And be manageable for you.