Thread: Need advice priming a fiberglass body

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The biggest problem with fiberglass is shinkage, where porous areas such as exposed fiber, will trap solvents keeping the paint swollen. Later, as the paint ages, the solvents escape, causing the paint to shink in those areas. Almost any 2-part primer should prevent this.

I have used Marhyde's "Ultimate Primer" daily for 15 years with zero adhesion or shinkage problems. It is reasonably priced, sands pretty easy, and has performed flawlessly.

On any metal surface, I metal prep 30 minutes before priming, eliminating the expense and trouble of using a self-etching primer. Again....zero failures.

I am a believer in "If it ain't broke, don't fix it". The only reason I would consider using epoxy under it, is if it was staying in primer indefinitely..... although I always thoroughly wet sand the primer, and have never had any rusting under the paint.

If you have kept the paint on boats, with the drag and pounding they get from the water, I would be confident with your system.