What paint should be used on fiberglass boat hulls?

Answer 1

You can use any type of automotive paint you want. The key to a good fiberglass paint job is the preparation.

Sanding and filling the gelcoat is the hard part. If it isn't a new truck box, thorough cleaning to remove grease and dirt is essential. If it is new, you need to fully cure it as discussed below. When sanding the gelcoat, make sure not to sand through to the fiberglass (if you do, fill and resand.)

Select a primer designed for the paint you have selected.

Warning about dark colors: they will cause the fiberglass resin to cure and shrink. If you are going to use a dark color, you want to bake the box in direct sun for at least a week, rotating it to give all sides direct sunlight. A light coat of flat black paint (which you will sand off) may help with the curing. If you have access to a large oven, that's even better. Expect to have to adjust the fit of the parts to compensate for shrinkage.

A custom car shop that hangs and paints fiberglass bodies should know how to do the job right. Custom marine builders and repair shops should have plenty of experience painting fiberglass also.

Answer 2

Marine epoxy paint should be used on fibreglass.