Here goes, it's pretty easy:
First, remove the rideplate - 4 bolts on a round, six on a square (plus you have to disconnect the old style siphon outlet on the square, but that's just a hose clip).
Next disconnect water line(s) and the steering cable (by pulling the outer sheath back and popping the connector off the ball joint).
Now you're ready to remove the pump: remove the 4 bolts clamping it up into the hull (make a note of the location of any shims that are in there). Then you have to break it free - they usually end up stuck to the hull, and there are some dowels that need to be pulled out of their locating holes. To do this lever the back of the pump downwards (a big screwdriver or similar will do the trick). With that done the whole pump can be pulled out backwards, removing the drive shaft spline from the midshaft (you'll have to pull back a couple of inches).
OK, now the hard part: getting the old prop off. It'll be stuck on there REALLY tight for sure. Don't try to do this without a spline holder and impeller tool (if you need one - some impellers have a nut-like part at the front). Clamp the spline holder in a vice with the driveshaft in it, and get a wrench on the impeller tool/impeller. It's a left hand thread, so you need to turn it clockwise looking down the shaft from the end of the shaft to the pump (towards the rear of the ski) to get it off. You'll probably need a big extension bar for the wrench, and you may have to heat the impeller to get it to crack free (say goodbye to your knuckles at this point).
OK, so now it's off and you need to clean up the threads, add some antisieze (do NOT skip this step) and wind the new impeller on counter clockwise looking towards the rear. You don't have to do it up that tight - the motor will do that for you.
Put the pump back in with the four bolts and shims as they were before. Reconnect the steering and water hose(s) and refit the rideplate.
Your done!! The hardest part will be getting the old prop off, but that's a matter of brute force rather than skill....
