Yep - I'm a boat guy too. Fiberglass is porous - even gelcoat - and problems can actually crop up from the inside. Nowhere is it more true than an ounce of prevention is worth a pound of cure. This boat is only 4 years old? I bet he stored it outside, without a cover. What a shame.
Sometimes the only cure is to sand and paint with an epoxy paint, which will hold up a lot better. Make sure whatever you use has PLENTY of UV protection. since it hasn't been mentioned yet I will also let you konw that
Meguiar's has a marine-specific product line.