With motor in forward, remove the 4 bolts holding the gearcase on. Shift into reverse. Gearcase will drop down slightly. Through the opening, you’ll see a 3/8" bolt which holds the lower shift rod into a coupler. While supporting the gearcase, remove that bolt. The gearcase will then drop down. The impeller is in the water pump housing on top of the gearcase. Remove the bolts holding it on and slide it up off the top of the driveshaft. Remove the old impeller and install the new impeller into the water pump housing. Slide the assembly back on the driveshaft and make sure the little pin in the driveshaft slips into the groove in the impeller. Bolt the housing back on, and reinstall the gearcase to the leg. Make sure the water tube fits into the grommet on the water pump housing. At the same time, make sure the lower shift rod slides into the coupler with the recess in the top of the shift rod aligned with the bolt hole in the coupler. Then reinsert and tighten the coupler bolt. Shift into neutral or forward and reinstall the bolts holding the gearcase to the leg.