Acetone won't disolve your boat!
Because acetone evaporates so quickly, I don't see any liklihood of it damaging the 5200 deck seal under the rubrail or anything else nearby for that matter. Its fast evaporation rate, though, makes it hard to work with, and its cousin, MEK, or other slower evaporating solvents are easier to work with. Acetone is the solvent that is used to apply and cleanup gelcoat, and definately won't harm gelcoat surfaces... in fact, it's a good surface cleaner for gelcoat stains.The way these things work, I believe, it by disolving a microscopically thick layer of the rubrail rubber, and dirt with it. That's why you have to whipe it off with a clean paper towel before the solvent evaporates and the rubber and stain can no longer be wiped away. They DO, however, disolve latex gloves also, so there is a possible problem with toxicity,( though this seems to be minimal with acetone, again because of its rapid evaporation rate). That's why I'm looking for a better and safer cleaner also.