47403 fuelab h e series twin screw pump|Fuel Pump Twin Screw EFI Electric In Unthreaded impellers and acorn nuts occur on motors with a threaded shaft. Correct rotation spins the impeller in a tightening motion, reversing the direction will allow the impeller to rotate in a loosening fashion. It is possible that the impeller and acorn nut can spin off in a matter of a few seconds if rotation is incorrect. Subscribe