Hello from JA My name is Woody. I will be glad to assist you today. I have been servicing ALL Major Brands of Appliances for 33 Years, and have over 100,000 in home repairs and over 50,000 phone and internet repairs under my belt.
Im sorry to say if you are holding the impellor and turning the bolt and the shaft is turning means the impellor is broken anf you will have to break the impellor off I normally use a pair of pliers and sqweeze it to break the plastic impellor
you can hold the motor rotor to remove the impellor , but you have to remove the pump and motor assembly from the dishwasher .
The best way is to just break it off and replace it ,the plastic had softened and allowed the impellor to just turn on the shaft it was originaly a D shape to lock it on to the shaft.
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