Don't waste power with a space heater, use a 100 watt light bulb in one of those "trouble lights".
You don't need to heat the whole space, just the engine itself. Put the light as close as you can to the engine block and preferrably some distance below the carburator so that the heat will rise past it and warm the fuel in the carb bowl.
That's what we did when we lived in Montreal and it worked well in those bad winters.
Hope this helps. No guarantees expressed or implied, use at your own risk, your mileage may vary, yada yada yada.
answered 3 years, 11 months ago
I stored my snowmobile in one of these last winter. The small amount of snow that got in surely wouldn't pose any threat to your space heater.