I also had 4 of these pumps (plus a smaller 650ish pump) that I connected to a Wavemaster Pro pump timer. Small AC
pumps with no start windings (which these don't have) can start in either direction, and they tend to start in the opposite direction than they were running when they last shut off (same as a electric rotisserie and microwave oven tray). That means these pumps will normally start up backwards. When they do, the blade can slide slightly up the shaft closer to the front of the cover where it hits a rubber baby buggy bumper, causing it to change its direction. the blade then slides back down the shaft towards the motor and avoids any further contact with the bumper.
That's all fine and good, until you connect them to a timer like you/I have. Then all this bumper bumping weakens the plastic cover where the bumper is attached, eventually causing the cover to break. All 5 of my pumps, including the small one have failed and although they are still in the tank, they now run backwards 1/2 the time.
My next pumps will be the DC
pumps, possibly Jabao WP pumps.
Hydor pumps are fine as long as you simply leave them on (or perhaps 1 cycle on-off per day). But I have a 100% fail rate within 6 months of being on a wave timer.