An isolation transformer eliminates any hardwire connection between the onboard AC power system and the dockside AC power system while maintaining enhanced integrity and electrical power by employing magnetic induction principles. The issue for boats connected to the shore power is that every one of them is connected to all the boats in the marina through the system's grounding conductor.
It creates the galvanic cell, which causes corrosion of less noble underwater metals, such as expensive aluminum outdrives. To help mitigate damage, sacrificial anodes are installed to corrode rather than galvanic cell metal. That is fine for a boat stored on a mooring and isolated from the dock.
Any boat plugged into the shore power contributes to the corrosion protection of all other boats. A boat with insufficient anode area is a drain to boats at the same dock that are properly equipped with adequate anodes. That is where a galvanic isolator comes in.
It does not have the same capability as an isolation transformer but goes a long way toward extending the service life of a sacrificial anode and mitigating corrosion. The isolator is much cheaper and has no significant weight compared to a transformer. A galvanic isolator boat is a necessity when regularly plugged into shore power. The isolator fulfills multiple roles in the boat's AC shore power system. One of the functions is to eliminate one galvanic cell component.
The installation involves connecting the green ground connector in series. Electrical continuity is necessary. The American Boat & Yacht Council has strict guidelines for addressing galvanic isolator standards. System amperage is typically 30 or 50 amps. The system has a series of design specifications to meet. New designs incorporate technology that identifies the units as 'fail-safe.' The designation ensures the isolator maintains safe ground continuity for a boat.