What Is a Galvanic Isolator?
A protective device that stops galvanic current coming in via shore power earth — the silent guardian of a yacht on the marina berth.
A galvanic isolator is a device fitted in series with the shore power earth line that blocks low-voltage galvanic currents while still allowing fault currents needed for safety. In the marina, boats can create an unintended battery circuit through the shore earth; a fault on a neighbouring boat or dissimilar metals can eat away at your anodes. The isolator breaks that circuit.
Without an isolator, the signs are typical: anodes gone before the end of the season and discolouration on underwater metal fittings. If your anodes are disappearing faster than expected, follow this order.
If anodes are wearing fast
First, carry out a leakage current test (is your own boat leaking current?).
Then check the galvanic isolator or have one fitted.
'Fit bigger anodes' is not a solution, it is just masking the symptom.
The next level up from an isolator is an isolation transformer: the isolator blocks DC, while the transformer removes the electrical connection altogether. A faulty isolator can fail silently; it should be tested periodically, or you should choose a model with a test indicator. For a boat left plugged in all year round at the marina, one or the other is essential.