How to Repair a Mercury 40hp Water Pump
- 1). Remove the negative cable from your outboard Mercury 40hp water pump's battery.
- 2). Remove the bolts that hold the upper and lower units of your Mercury 40hp together. Get a good hold on the lower unit as you loosen it and remove the final screws so that the lower unit does not fall. The bolts can be removed with a socket set.
- 3). Lay the lower unit on a work bench or other flat surface and remove the four retaining bolts that clamp your water pump down in place on the drive shaft. Slide the water pump up and off of the drive shaft. Use a flathead screwdriver if necessary to remove the top of the water pump, which will reveal the impeller.
- 4). Push the old impeller out or work it loose with a flathead screwdriver. Slide the new impeller in and replace the top of the water pump.
- 5). Slip the retaining bolts through the holes on the water pump casing. Align them with the mounting area on the drive shaft and tighten them down completely.
- 6). Re-connect your lower unit to the upper unit. Replace your negative battery cable.
