Finally got around to doing one job that I wanted to get taken care of last fall. Change out the water pump and impeller on my 2000 Mercury 150HP XR-6. I see the question pop up here every once in a while asking how hard of a job is it to do. My reply is – if you can change out the front brakes on your car, you can do a water pump/impeller. My owners manual recommends changing the impeller every 100 hours or once a year. I have been doing mine every other season of use and don’t feel I’m stretching my luck.
Here is a before shot:
First thing to do is go to you dealer and purchase a water pump – impeller kit. Make sure to get the entire kit with all of the gaskets, not just a new impeller. It’s my opinion that you may as well change out all of the parts rather than just swapping out the impeller. Why not do it right since you have the lower unit torn down anyway? My kit cost about $40.
Once you have the kit which contains the pump housing, gaskets, pilot tube and impeller gather the necessary tools. All you need is basic tools such as a socket set, screw driver, rubber mallet and of course a cold one! It’s also a huge plus to have an extra set of hands. In my case I had Gary Wellman over to tackle this 6-pack job.
First and most important – Put the motor in FORWARD gear.
Next, remove the zinc alloy disk and expose one of the retaining bolts under the cavitation plate. Working around the lower unit, remove all of the bolds being careful not to let the lower unit drop to the floor. (This is where a second set of hands help out) Once all of the bolts are removed, a few taps with the rubber mallet will separate the lower unit. You may need to separate the water line that operates your speedometer at this point too.
A bench vice is very helpful to hold the lower unit in place while you remove and replace the parts.
Start out by removing the 4 nuts that hold the pump housing in place.
Apply firm upward pressure until the pump housing separates. Slide the pump housing and impeller up and off of the drive shaft.
Here is a look at the old pump housing and impeller.
Old and New impeller.
Next, remove the gaskets and keep them in order so you can use them as a guide when replacing the new gaskets. My pump has 3 gaskets.
Replace the new gaskets in the exact order and configuration as the old one’s were removed.
Note the location of the retaining key for the impeller. Slide the new impeller on to the drive shaft and over the retaining key. This will prevent the impeller from spinning on the drive shaft.
Next, slide the new pump housing down the drive shaft and while turning the drive shaft in a CLOCKWISE direction, press the pump housing over the new impeller.
Replace the 4 nuts securing the pump housing in place.
Next, place the new pilot tube in the pump housing, and slide the new “Slinger” gasket down the drive shaft sealing up the water pump.
Now, with your extra set of hands, line everything up and slide the lower unit back onto the motor. You may find that you will need to turn the drive shaft slightly in a clockwise direction to line up the splines to the power head. Make sure your shift linkages are in place and reconnect the speedometer line.
Replace all of the bolts and tighten everything up. Drop the motor out of gear. This will tell you if you have the shift linkages hooked up correctly. The prop should spin freely at this point.
A final touch up of new paint and she is good as new.
When you first run the motor, check for water flow out of the pee hole. You are done! Now finish off that beer!
i personally owe you one 
