4 mm ply lapstrake canoe. Garboards exterior and garboards plus first strake are covered with fiberglass. Same expoxy over all, roughed up the same. On the wood covered with epoxy, Rustoleum self-priming paint adhered fine. On the fiberglassed areas, bubbling is developing in places.

I can't see why there is any difference in the surfaces the paint is bonding to. Any idea why this is happening?

I can strip the areas that the paint is bubbling on and repaint. First, I need a solution to the bubbling. Would a primer reliably allow the topcoat to stick without bubbling? Any idea what primer? Is this a good solution? Anything else I might consider?