Dirk,

Here's what most likely happened. The old gelcoat was most likely bad which means porous. So it was painted. You decide to re-gelcoat. Ok, but the paint's chemicals have made thier way into the pourous gelcoat contaminating it. Meaning even though it appears the all the paint is sanded off some must have remained. Gelcoat will always react when applied over any paint. Wiping the boat with acetone before spraying was not a good idea in my opinion. I would never use any chemical to wipe after sanding. Soap and water and a tack rag is it. Just a lot of chemicals there. I might of missed it when reading some of the earlier posts but when I said re-gelcoating was fine I didn't know that the boat had been painted. Knowing that I would of just repainted if I were you.

Also understand these chemicals take time to cure. Its not surprising that it took a couple of weeks to show up. I only hope the chemicals have used up their energy so this does not happen again.