do i need to primer before paint?

[revshot]

ive got my boat sanded down a layer, i was initially going to primer the boat then spray the topside with an automotive 2 stage paint. (the paint was free) after sanding it smooth and filling in the gouges ext.. i realised i never needed to sand through the original gel coat, so there is no bare fiberglass exposed.

do i still need to lay down a high build primer or can i just spray the paint overtop of the sanded gel coat and expect a similar quality?

[Deering]

Depends on the paint - I would consult with the manufacturer. But with a polyester resin substrate (gel coat) I would expect that you'd need a primer to ensure good adhesion.

[ondarvr]

Most 2 part paints bond very well to unprimed gel coat, I've never had bonding issues (25+years) when not using a primer on gel coat. If you are painting the hull, and this boat is left in the water for long periods of time, you might want to use a paint and primer designed for that purpose. For a trailered boat, what you have will work.

[wdnboatbuilder]

Pettit makes a Epoxy high build primer that is made just for painting gel-coat. the only problem is they only make it in a gray color which I think sux.

[jimslade]

I would use an epoxy primer. I don't recommend anyone spraying any paint that uses isocyanates as a hardner unless it's in a spray booth and using a proper air mask. If by 2 stage paint you are referring to base/ clear you have to make sure that the surface has a good sealer and prepped very well or the base color will show through after a short time in the sun. There are many top coat systems that are less toxic to use than 2 stage paint systems.

[paulfox74]

I just came across this site and started sucking in info, so I thought I would give some back. I paint aircraft for a living and have restored a 78 allison gt20 . While this no way makes me a expert I do Know if you want a good finish you need to prime,resone being that you will get teligraphing,that is the high and low areas bleeding through.this may not show right away but when the sun fully cures the paint,1month 2months? you will see it.make sure you hand sand with 320 are higher after the primer has cured and do not break through.