So far we had to lift out Polaris every 4 months to change the saildrive anodes. The zinc anodes eroded with shocking velocity. Portsmouth Harbour with its Navy ships is notorious for that.
So, in my boat maintenance course I learned that a galvanic isolator might be the solution. Here is how it works. Electrons from electric currents follow the way of least resistance to the ground. Electrons in an electrolyte such as seawater flow through the boat’s anodes and the shorepower line to the pontoon’s electrical ground. thereby eroding the anodes very at record speed. A galvanic isolator blocks all small electrical currents typical for galvanic corrosion. Yet it lets pass any undue high current coming from a malfunctioning electric device on the boat.
I will update this page with the results in the future.
After one year in use the galvanic isolator appears to slow down the corrosion of the anodes. Instead of 4 lifts this year we reduced to 3.
Update November 2021: We are now down to a very reasonable wearing of our anodes. One change per year, usually during the spring lift out, is enough. We have reduced to two lift outs per year. One in spring, to prepare the hull for the season, i.e. pressure washing off the fouling and to check / change the anodes. The other one in autumn when, besides to pressure washing the hull, we also service the sail drive.