Abstract: Pumps, for example, bilge pumps, comprise a pump housing including an inlet and an outlet, a motor and an impeller assembly coupled to the motor for pumping liquid which passes through the outlet. The motor is advantageously cooled by pumped liquid while being protected from the pumped liquid. Further, the motor is turned on and off in response to actual operating conditions, thereby increasing pump life and reducing overall power consumption. The pump provides contoured facing surfaces which provide a dynamically efficient flow path for the pumped liquid. In addition, a switch housing is preferably provided to allow liquid to contact an activator assembly which turns the motor on.