Question
How do I remove the diffuser/impeller? I am replacing a cracked iron bracket for a Water Ace sprinkler pump (2hp)

Answer
Thanks for your question.
Obviously you will need to open the pump casing and I'm assuming you already have that done.
The impeller is screwed on to the motor shaft. You will need to open the back of the motor. There is a (usually) 7/16 slot on the shaft where you can use a wrench to stop it from rotating. You may need to move the starting capacitor to access the slot. (That's the round black thing about 3" long) Once the shaft is locked, you can remove the impeller by unscrewing counterclockwise. Under the impeller is the shaft seal. Be very careful with it, they are fragile. It is just pushed on and the other half is in the case, pushed into a rubber mount.
This will make more sense to you once you see the pump opened. I've included a owners manual web link, with parts breakdown of the pump. It should help.

Matt

http://www.waterace.com/pdf/R7L%20R10L%20R15L%20R20L%20and%20R25L%20Lawn%20Sprin...