Since I'll be going through Lake Champlain in a few weeks, I'm wondering where in Danby VT you keep a 36' boat. Looks a little hilly on the map
But seriously, the first step in diagnosing thruster problems is to listen. The click means there's power to the windings of the solenoid, so that rules out one whole side of the wiring. Some possibilities are posted above. Also look for a popped breaker. A big voltage drop on the system that powers the thruster would indicate the motor is getting power but is locked for some reason. No voltage drop means no power to the motor. Don't neglect the ground side of the circuit, that seems to be the problem more often than not. Also consider loose connections that can test OK but fail when a load is put on them.