Cummins/Onan — Replacing the Raw Water Pump Impeller
Maintenance
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan MDKB, Cummins/Onan MDKBH
Before you start
- Do not lubricate the impeller with grease or oil or other petroleum products.
Procedure
- Close the sea cock and disconnect the negative battery cable.
- Remove the front and top access doors; remove the end panel if work space is limited.
- Loosen the hose clamps shown and disconnect the hoses.
- Loosen the two pump mounting bolts and remove the belt.
- Remove the tension adjusting bolt, swing the pump out and remove the pivot bolt; pull the pump out.
- Remove the 4 pump cover screws and remove the impeller and O-ring.
- Install the new impeller, twisting it clockwise while squeezing it into the housing.
- Wet the inside of the pump and impeller with water, soap solution or a silicone lubricant.
- Secure the cover and O-ring.
- Remount the pump, reconnect the hoses, adjust V-belt tension and reassemble panels and doors.
- Fill the sea water strainer if above the water line, open the sea cock, reconnect battery cables (negative last) and start the genset.
Tools required
- two pliers Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Full service-parts list: Cummins/Onan MDKB →, Cummins/Onan MDKBH →
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.