Impeller 396725

Function and Technical Context

The impeller 396725 (replacement reference REC396725) is the rotating rubber element housed inside the raw water cooling pump of OMC engines, whose function is to generate the continuous water flow that circulates through the engine cooling system. When rotating inside the pump housing, its flexible vanes create a pumping action that draws water from outside the vessel and forces it through the engine block, dissipating the heat produced during combustion. When the rubber vanes crack, deform or break away due to wear, the volume of water pumped drops critically, exposing the powerplant to severe overheating that can result in permanent damage to the cylinder head gasket, block or bearings. Manufactured to fit precisely in the water pump housing of OMC engines, this impeller ensures optimal sealing and pumping performance from the first startup.

When Should You Replace This Part?

The clearest signs that the impeller has reached the end of its service life are the decrease or disappearance of water flow from the discharge pilot ("tell-tale"), the rapid rise in engine temperature during navigation and the presence of black rubber fragments in the cooling circuit. Marine manufacturers and technicians recommend replacing the impeller every 200-300 operating hours or, at minimum, once per season, since the elastomer ages and loses elasticity even during extended periods of inactivity. Including this replacement in the seasonal service is the most cost-effective preventive intervention to avoid an overheating failure at sea and the expensive repairs it entails.

Compatible Johnson/Evinrude Engines

Equivalent Manufacturer References