My Hayward Super Pump (1 1/2 HP) began making a loud rattling noise very similar to cavitation (sounds like rocks in the impeller). It seemed to get worse and worse until finally I just couldn't run the pump because it was so loud. The water flow (circulation) was fine and I couldn't notice a difference. I pulled the motor/impeller assembly yesterday and the impeller doesn't spin easily and makes a scrapping sound when I turn it by hand so I'm guessing this is the problem. I was wondering if any one could give me ideas about what the exact issue could be.