As all of you know, I had some corrosion issues with my Aluminum Hulled Kingscraft. I finally got the electrical rewired and corrected. I took some readings again and I am now trying to determine what other steps that I need to take.

I used the reference electrode from Boat Zincs to take my readings. In their instructions they state that my Hull Potential should be between -900mV and -1200mV. While unplugged from shore power, my boat's reading is -1050mV. When plugged into Shore Power, my reading is -588mV. That is well out of the range for adequate protection. After unplugging a neighboring houseboat, whom we know has electrical issues, my reading is -800mV. I am still -250mV from the reading when I am unplugged. I believe there are more offenders at my dock contributing to the issue and I am going to address it with the marina. However, I have a couple of questions about the galvanic isolator. Should my readings be exactly the same from unplugged to plugged in with the GI installed? Would I still see the large difference in Potential even with the GI installed? I am going to give today to discuss this as well.