Pool pump noisy, but no prime

[jonneeboy]

Have a 2 HP Hayward pump. Disassembled and cleaned impeller. Now trying to put it back together and the impeller threads will not seat on the motor shaft. They are acting as if either the threads on the shaft or the the threads in the impeller are stripped.

Can this happen? Does it indicate a larger problem? The motor shaft turns freely.

I am hoping I can just purchase a new impeller and replace, but dont want to ignore a larger problem.