Raw Water Pump Impeller

[Ken Juul]

Somewhere, probably on the Message board, I read that it doesn't matter which way the impeller spokes are aligned when the impeller is installed, they will self align on the first rotation.  A helpful tidbit of information, but is it correct?   I am happy to report that it is spot on.

Over the weekend a dockmate asked for help.  It was his first impeller change.  His engine has a belt driven pump, so it is easy to see how the impeller reacts inside the pump casing.  I pulled his old impeller off, reinstalled it with the spokes in various directions.  I then turned the pulley, watching the spokes seek the correct alignment.  They slid easily in place.  I reversed the spinning direction, in one revolution all were aligned in the new direction.  I did this with a dry pump, even with a worn out impeller it did not appear to put excessive stress on the spokes.  Much relieved that spoke direction didn't matter, my dockmate, confidently installed his new impeller.

Something good to remember when you are doing an emergency underway impeller change!

[Stu Jackson]

This question was raised recently on another board.  FWIW, our Oberdorfer runs clockwise (easy to remember - just look at your watch, if you still have an analog one!).