Hoffman Jacket water heaters, such as part # 375-4743, are electrically operated immersion heaters fitted to the water jacket surrounding the cylinder block of an engine to warm the coolant in cold weather. Jacket water heater Thermostat preset to 54° C (130° F) Standard Thermostat Range: 38° C - 54° C (100° F - 130° F) Heater Ratings: 208 VAC, Single Phase, 9 kW Pump Ratings: 208/240 VAC, Single Phase, 10 GPM, 60 Hz, 97 W Length: 527mm (20.76 inches)