Impeller replacement

by Bob
(East Hartford ,ct)

My Dolphin diagnostic has a broken impeller blade , I've ordered a replacement and am trying to reome the old impeller blade off of its shaft . I've removed the center screw holding the impeller unit on its shaft but the unit will not slide off the shaft, I've heated it with hot water with no luck still, is there something else that holds the impeller spinal in place?
ADMIN REPLY: I have used a large flat screwdriver. Place the screwdriver blade vertically under the impeller. Using the case for leverage i will strike the handle sharply with my hand. impeller pops off.