Rebuilding water pumps once a year or every 100 hours is the best way to ensure these pumps are working at full capacity. Check with your marine dealer for the specific rebuild kits you’ll need for your particular model of engine and lower unit.
Raw-Water Intake Pump
1. Removing the Raw-Water Intake Pump
After draining the cooling water, loosen the hose clamps and remove the inlet and outlet hoses. Loosen the drive-belt tension and remove the belt. Remove the mounting bolts and remove the pump from the engine.
2. Removing the Impeller
Mark the alignment of the mounting bracket, bearing and shaft housing. Note the location of each bolt, washer and nut, and remove them. Pull the pump body from the shaft and bearing housing. Remove and discard the old impeller and wear plate, as well as old gaskets, O-rings, seals and impeller key, based on new items provided in the rebuild kit.
3. Installing the Impeller
Install the new wear plate, gaskets, O-rings, seals, impeller key and impeller, applying a light coat of grease to each. While turning the pump shaft clockwise, push the pump housing to seat the vanes. Rotate the pump body to align the marks, and install the mounting bolts, washers and nuts. Reinstall the pump.
Lower-Unit Pickup Pump
1. Removing the Lower Unit
You will need to shift into either forward or reverse in order to demount the lower unit, depending upon the model and rotation of the drive, so check the manual. Remove the propeller, the prop hardware and the bolts holding the lower unit to the midsection, including the one hidden under the trim tab/anode. Also, disconnect the speedometer tube. Carefully pull on the lower unit and drive shaft from the midsection. Depending on the model, the shift shaft may be attached to the lower unit. For a step-by-step guide, go to boatingmag.com/maintenance/diy-projects/replacing-stern-drive-bellows.
2. Removing the Impeller
Remove the water pump housing bolts, and pull off the housing, impeller and wear plate, sliding them up and off the drive shaft. Discard gaskets, O-rings, seals, housing liner and the impeller key based on new parts in the rebuild kit. Check the drive shaft for wear where the seals ride, and if worn consider replacement.
3. Installing the Impeller
Grease and install the new parts from the rebuild kit. Grease and slide the impeller down the drive shaft, aligning it with the key and seating it against the wear plate. Slide the pump housing down the shaft. While turning the shaft clockwise, push the housing over the impeller, securing it with the housing bolts (brush threads with anti-seize compound). Reinstall the lower unit.
Quick Tip: An inboard or sterndrive may also have a belt- or shaft-driven water circulating pump on the front of the engine, and this is usually replaced with new or rebuilt units when it wears out. Pump prices range from $74.95 to $209.95. Two companies offering such pumps include Doug Russell Marine dougrussell.com and Michigan Motorz michiganmotorz.com.
A properly functioning cooling system is critical to marine powertrain reliability. Water pumps serve as the heart of the system. Some sterndrives have a lower-unit pickup pump in the drive (same as an outboard), and others have an inboard raw-water intake pump, either belt-driven or direct drive (same as most inboards).
