If you're normally a continuous cruiser, but are spending time in a marina, don't forget that while your boat's hooked up to an electric point, you absolutely need to protect the boat from Galvanic currents.
Of course, this applies to ANYONE who plugs into an electric point, whether it's a marina or an on line mooring.
Glavanic currents can corrode your boats hull, prop and sterngear, and eat away at your anodes. And all this can occur a lot faster than you might think. A Galvanic isolator STOPS this from happening.
To fit a Galvanic isolator takes a few seconds - you just plug it in. There's no wiring in needed.
For more info, and to buy, please.... 
