primer purpose
I'm no paint expert but as I understand it, the purpose of the primer is to ensure there is a good substrate which both chemically and physically bonds to the hull and, in turn, to the paint subsequently applied. If one coat does that, there appears to be no purpose in doing more. Having said that, there are only two absolutes here: 1. Follow the mfgs recommendations, and 2. always use the same mfg's components, i.e., same mfg primer and paint, to ensure proper adhesion. There is an excellent treatise on priming and painting hulls in this month's Practical Navigator which you might want to read before going further or getting expert advice.
