Cummins/Onan — Sea Water Pump Assembly
Repair & overhaul
From a Cummins/Onan service manual covering: 2.5 MAJB-53BR, 2.5 MAJB-53CR, 3.0 MAJB-1R. Check it applies to your exact model before use.
Applies to: Cummins/Onan MAJ, Cummins/Onan MAJB engine
Before you start
- Never operate a neoprene impeller pump dry
Procedure
- Press the bearing over the pulley end of the shaft far enough to clear the shaft retaining ring groove.
- Install the new water seal as shown; lubricate surfaces; seal surface must be just below the edge of the impeller body.
- Install the plastic washer and O-ring over the impeller end of the shaft.
- Press the shaft/bearing assembly into the pump until it bottoms against the pump body.
- Install the bearing and shaft retainer rings and the plastic end cap/seal.
- Install the wear plate in the impeller chamber with the notch over the locator pin.
- Install the cam and cam set screw with one copper washer under the screw head.
- Lubricate the impeller with vaseline, fit it in the direction of rotation, install gasket, end plate and screws, then pulley, belt and belt guard.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Full service-parts list: Cummins/Onan MAJ →
Source: Cummins/Onan service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.