We don't have an electrical bonding system on our Catalina yachts, right? They don't work well in marinas, and we don't need them with our non-metallic thru-hulls, right? My zincs are only lasting 3 months, and a marine electrician wants to charge $255 to check out my bonding system. He's trying to rip me off, I think. All I need is a galvanic check?