Best deal on Johnson Heavy Duty Electro-Magnetic Clutch Pump. Pumps with Electro-magnetic Clutch.. Clutch pumps combine the advantages of the self-priming flexible impeller pump with a clutch drive mechanism to engage or disengage the pump as needed. Marine Engine Cooling Raw Water / Seawater Pumps, Flexible e Bronze Impeller. We supply engine cooling pumps to the world’s leading marine motor manufacturers,. Raw Water e Engine Cooling Pumps, Bronze Engine Cooling Pumps. Raw water (river water or seawater) is pumped directly through the cylinder block, exhaust manifold or exhaust silencer. The raw water flexible impeller cooling pump can be pulley, gear or crankshaft mounted.