It was probably painted to hide some deep scratches. When you get off the finish coat of paint i suspect you'll find some filler, or lots of scratches which are filled with paint. If so, you'll have to sand the entire boat deep enough to remove them.

A chemical based approach, which would soften the paint in those tiny scratches, or maybe gentle heat, might be more productive than sanding. Try an inconspicuous area and see what happens.

Why bother? If the paint appears to be holding on firmly, scuff it up with some medium sandpaper and repaint the boat with a glossy enamel. A colored polyurethane will give you a very tough finish. You can test an area to see if there are any incompatibilities before you commit to doing the whole thing.

PGJ