As background to my question, I have a Freedom 21 with the fin keel. I imagined that the lead keel (700 pounds) was encased inside the fin by fiberglass. I have installed a 120 volt AC shore power system and a on board DC system. The freedon 21 has a carbon fiber mast that a PO has connected, with a heavy wire, to a keel bolt. As far as I can find out this connection is not factory standard.
Question:
I measured the DC voltage from the keel bolts to a shore power extension cord ground lead and it was 0.7 volts.. I also measured the DC current, but found none using a DVM with a 200uA scale. So I imagine that the impedance of the keel to salt water must be very high.. Also the AC and DC system grounds are connected together and then to the keel through the shield on the mast VHF antenna whose mount is screwed into the carbon fiber mast.
Do I need to install a galvanic isolator, given that the boat is at a private dock with no other boats on the shore power? Also do I need zinc on the keel--There are hundreds of these finned keeled Freedom 21's and none have zincs installed.. There are no other thru hull metal objects on my boat (has an 4 HP outboat aux.)
Question:
I measured the DC voltage from the keel bolts to a shore power extension cord ground lead and it was 0.7 volts.. I also measured the DC current, but found none using a DVM with a 200uA scale. So I imagine that the impedance of the keel to salt water must be very high.. Also the AC and DC system grounds are connected together and then to the keel through the shield on the mast VHF antenna whose mount is screwed into the carbon fiber mast.
Do I need to install a galvanic isolator, given that the boat is at a private dock with no other boats on the shore power? Also do I need zinc on the keel--There are hundreds of these finned keeled Freedom 21's and none have zincs installed.. There are no other thru hull metal objects on my boat (has an 4 HP outboat aux.)