I recently bought a 1971 S&S Swan. The hull was epoxied with a barrier coat, faired, and then painted with Imron. The paint has little bubbles that when punctured weep a dark liquid with a strong chemical smell. What could this be? The deck is partially painted with the same paint but the parts that are not covered are chalky. If I rub my hand over the deck, it leaves a whitish spot. I'd like to know if the deck paint can be removed and the deck restored to the original surface?
Tom Wood responds:
You don't state where on the hull these blisters occur, whether above or below the waterline, but it sounds suspiciously like osmotic blistering. Those blisters with the dark brown odiferous liquid are a giveaway. Be very careful popping the blisters as the liquid is highly toxicwear eye protection and rubber gloves. They are rarely found above the waterline unless the laminating process was grossly inferior (unlikely with such a pedigree) or the hull is completely waterlogged (possible with a 28-year-old-boat). It is possible that the fairing compound used under the Imron was of poor quality. A moisture meter would be valuable here, but the readings are not reliable until the boat has been stored in a dry area for a few weeks. It is important that you discover if the hull's water absorption is affecting the structural integrity of the fiberglass or if it is merely surface entrapment.
If it is pervasive, the boat should be hauled and stored long enough to dry completely. All surface paints and fillers should be removed and the hull coated and repainted when drya major task at best.
If it is the latter, then it is merely cosmetic, and these always pose difficult choices. You can simply leave it the way it is, of course. Merely recoating over the old paint will give you temporary relief, but the problem will undoubtedly recur in a few years. Or you can remove the old paint and filler, and do the job again.
On the deck, the old gelcoat has become porous. If the Imron on the painted portions is in good condition, it need not be removed. With some preparation, a new coat of paint can be laid on top of the old. If you're not actually sure that it is Imron, or another two-part polyurethane paint, a barrier primer coat should be used. On the unpainted portions, remove it with rubbing compounds, beginning with coarse and progressing to fine, followed by a good coat of wax that will give you a temporary shine. But as badly chalked as it sounds in its old age, it won't last long. It smells like a whole new paint job to me.