We have got a steel boat, two engines (isolated from hull), a separate electric system (batteries) for engines & one for services and 12V on the hull.
Everything seems proper insulated but still, we have 12V on the hull. When both electrical systems are switched off, we still have 4V. We have been testing everything with the voltmeter and the ohms as well. Any suggestions what we can do or which of your books is best for steel yachts,( the fishing, or the yachty book) ?