Abstract: An engine heater is provided for installation in a liquid-cooled internal combustion engine. The heater includes an electrical resistance heater element and a pump driven by an electric motor to circulate heated fluid through the engine. A thermostatically-controlled switch in thermal contact with the housing may be provided, to shut the device off when the temperature of the device exceeds a predetermined level. The heater may comprise dual resistors housed within a helical sheath that surrounds a direct-current ("DC") pump motor housed within a watertight pump casing. The motor drives an impeller positioned externally to the motor casing. An array of anti-swirl vanes are positioned within the housing extending outwardly from the motor casing adjacent to and downstream of the impeller to guide the flow of fluid and prevent it from rotating with the impeller.