Ok what belt do you run? The larger diameter might slow the pump down bit but that is the only effect. That pulley is designed for a belt that measures 1/2 inch across the back side. If the belt you have or had measures 1/2 inch across the back it will work. If the belt is wider it isn't going to work .
It took less than ten minutes to press the hub down and cut off the shaft. When they rebuild the pump they have to pull the hub off and press it back on.
Start to finish I laid both pulleys on the bench and laid a straight edge across the long one, measured the difference between it and the short one with a machinist's rule, set the pump in the press with the impeller hub sitting on a flat piece of steel, moved the hub a bit and measured, moved and measured until I got it where I wanted it. Cut the shaft off to match what had stuck out before, beveled the end with a file just a bit and installed it. This is the one I did 35 years ago that I took a photo of a few months ago.
