I am constructing an autonomous, unmanned boat for voyages of several months. Traditional autopilots use a linear actuator to move the tiller but require several adjustments per minute. They will consume a lot of electricity and probably wear out mid-voyage. We are looking at wind-vane designs to steer the boat. Wind-vanes are able to steer for great distances without adjustment. The boat will be approx. 5m in length.
In the image below, the 'Course Setting' is done by manually rotating the wind-vane and dropping a pin to hold this position of the two discs. We need a way to rotate the vane fairly precisely and then lock it into position. We are using 12V DC. After it is locked, it should draw no power.
As you can see, the current design (not our drawing) would have any electromechanical mechanism hanging off of the end of the boat and attached to the rod of the trim tab.
Is there anything we can use to turn and then lock the wind vane in place? Preferably something that could be proofed against wind and water.