XTREME Heater 600. Bilge heaters built with new technology makes Xtreme the smart choice for the serious boater. BTU: 2050 to 2725. Cubic Ft: 675. Wattage: 600-800plus. Exit Air Temp: 245. The core of the Xtreme Heater is a heating element that is self-regulated at a preset temperature and automatically varies its wattage in order to maintain that …