I had the same sound a couple weeks back and it turned out that my centrifugal switch was stuck. I have a Hayward Super II Pump, so I am not sure what yours looks like behind the back cover. I am not a pump mechanic, I just tried this and it worked for me so no guarantees. First make sure the power is off. If you can get the back cover off, look for an inverted "V" shaped device. If you have one, try wiggling it a little by hand...gently back and forth. Mine was stuck and after a little help, it began moving easily and the pump worked fine. If it's not that, your impellar might be stuck, once you have the front of the pump off (with the power off of course), try turning it by hand a little. It just may have gotten stuck in the offseason. Hope this helps a bit.