Argh. Spent all morning taking the pump apart. Tried to undo the impeller by holding the shaft with a wrench and ended up breaking the centrifugal switch.

Drove 30 miles to buy a replacement. Now I have the 7/16 wrench holding the shaft from the bottom but just cannot get the impeller off. Tried using strap wrench and channel pliers, no luck.

Any other ideas? (I'm going counter clockwise).