The impeller normally slides right up the shaft. The clearance between the impeller sleeve and shaft is maybe .010 to .015. Salt deposits and crud can build up and cause the impeller to lock to the shaft. Before I try to lift the impeller up the shaft I will use some emery cloth and polish the shaft from the impeller to the shaft splines at the top of the shaft. I then use a small wire brush and clean any build up on the top of the impeller. I use compressed air to try to blow any debris that was loosened up when cleaning the shaft and top of the impeller. Using a small amount of oil or penetrant to seep into the area between the impeller sleeve and shaft, let that soak for a minute or two then grab the impeller in one hand and hold the shaft in the other and try working the impeller back and forth to free it up. There is a key in a keyway that drives the impeller. If it was sitting proud when the impeller was installed (factory install many times are) this will add to the difficulty of lifting the impeller up. Normally once it breaks loose it will lift up easily. In worse case conditions I have used two small pry bars to help lift the impeller. Use protective softeners (rags) to set on the top of the housing and impeller wear plate. slide the pry bar tips under the impeller carefully ( If you are replacing the wear plate, which I would) you don't need to be as careful. lift up with the pry bars and the impeller will then slide up the cleaned shaft. Remove the key out of the key way when the impeller is off. Clean the keyway and install a new key into it with some grease. Make sure the key is completely seated so the next time you replace the impeller it is not as difficult. I also apply a small amount of anti corrosive grease shaft to impeller mating surface. ( do not use anti-seize use a good marine grease) This will help in the future. Good luck!
