There is a discussion going on over on one of the boat discussion groups about elevator style lifts that have metal in the water all the time. When this is connected to the service grounding electrode system, it tends to become the best electrode and if the metal is aluminum, it will erode away.
There are lots of ideas about how to legally mitigate the problem. The easiest one is to simply unplug the whole thing when it is not being used but that still leaves it connected when you are out in your boat. That mitigates most of the damage but not all of it. My first thought is why don't they use double insulated motors so they would not need the grounding conductor in the first place but those motors do not seem to exist in normal circles. (120/240 6 wire motor at 1hp or so).
The other thought is a 3 or 4 wire contactor/switch that disconnects all wiring when the motors are actually running as part of a "Gem" style controller. (uses a gate opener clicker)
Any thoughts here?