Six years back I was having both shaft zincs disintegrate in about 3 months. I got a corrosion Reference electrode from BoatZincs.com. It was very helpful in figuring things out and a good way to determine if you anodes need replacing with out needing to see them. Turned out that the culprit was the keel. If the sealing paint on the keel is no longer so good it will do that. My research revealed that a lead keel does not need galvanic protection so I disconnected the grounding wire to that front keel bolt. The keel is still connected to the mast and stantions for lightning protection but not the motor and shaft. I have inspected the keel from multiple haul outs and there has been no issues.
