A boat that sits in the water, will be about the temp of the water due to transfer. SO if the water stays warmer then the air, the drive train should not freeze. Our local lake does not get below 50* during the winters. We have marinas full of slip'd boats that stay in the water year round. So if you feel that the boat will not freeze sitting in the water, all you need to do is all the normal services minus the water draining.