I have blocked the movement of the motor shaft. It is not turning. The impeller is turning on the motor shaft, but it is not coming loose. It is just turning on the shaft. Not freely turning but hard to turn..

I think the proble is the threaded insert in the impeller is turning inside the impeller rather than loosening from the shaft.

It appears to me the impeller will have to be cut off or broken with a hammer or something to get to the threaded insert.