I don't think it will blow heat for very long without coolant circulation. The Heater Craft heater is ideal for motoring underway, so it might be just fine if I were to take it down the ditch or just for motoring to my winter haul-out on a chilly late-fall day.

Other than that I would probably still use the Coleman Black Cat to take the chill off the cabin in the early morning. It's adequate for high-thirty+ temps. We're not cold weather sailors so an Espar isn't justified at this point. For rare occasions we could run an electric space heater periodically with my (dare mention it?) 2000w inverter generator. In some places, if it's really cold we could take a slip and plug into the grid (but we've yet to have the need).