I have a similar situation here but after talking with several folks including the techs at our Marina, everything should be OK when you are wet slipped (I think Chuck is wet slipped) because the water temperature is always in the 40s or above for the most part. In the event of a prolonged outage, you can start your motor and let it fully warm up. When you turn it off the heat from the motor will keep things warm enough for at least a day. It takes a prolonged drop of below freezing temperatures to damage an engine. If there are ongoing concerns about below freezing temperatures with no power, then I plan to drain my block too just to be on the safe side. If you store your boat on a trailer outside, then you really can't rely soley on a bilge heater in the event of a power failure.