O-320(except H & rear carb), O-360, O-470, IO-470
O-520, IO-520, TIO-520, O-540, IO-550, TIO-550
300 watts or less / Thermostatically Controlled
3 to 5 hours on cold soaked engine, although, since unit is thermostatically controlled, it may be left on overnight, or all the time. Cowl covers and prop covers are recommended for extreme cold weather, They also reduce preheat time.
3 3/4 x 5