I lived in North Dakota most of my life. started many large diesel engines in very cold weather. I don't like the WD-40 idea, some do. the space heater is a good direction but not so fond of the heater in a cold boat idea. I like the shore power and heat the hot water heater. as well as a heat lamp an infrared bulb for 12 hours the engine will be toasty just like the summer. open the engine compartment and shine the light on the block. no ignition source and it will warm the block. It works in the shed in sub zero conditions. just block the wind and inside the cabin should be no wind over night. good luck.