I purchased a used Wavebox 6212 here on RC. I'm having a problem with the pump, even after cleaning the impeller. On the timer, the pump seems to start up properly about 60% of the time. The other 40% it chatters and doesn't really turn over. And, the impeller blades look a bit beat up. Does all this indicate it might need a replacement impeller? Or, maybe a need an overhaul from Roger?