Oberdorfer Impeller Replacement

[scgunner]

      I just finished my 100hr service on my M-25 which always includes replacing the Oberdorfer raw water impeller. I don't know about you guys but I've always found this operation to be a pain in the arse. Sometimes it goes fairly smoothly, most times not. This was one of those not times. The impeller went almost all the way onto the shaft and stuck. What to do? I consulted to manual which said if you remove the shaft you'll have to pull the whole pump to reset shaft. I went ahead anyway and pulled the shaft with impeller attached. On the bench I was able to properly set the impeller w/ circlip on the shaft. Then I used a zip tie to compress the impeller vanes, I was able to slip the shaft right back in, removed the zip tie, done and done.
       Going forward I think this is how I'll do it from now on, this method allows you to R&R the impeller on the bench and the slot end of the shaft fits in similar to putting a distributor in an engine block

[Stu Jackson]

Kevin,

Here's the answer, with photos.

http://c34.org/bbs/index.php/topic,6766.msg45766.html#msg45766

[KWKloeber]

Read the techwiki article about the pump and the circlip. Take it off and throw it away and make an emergency change out easy for yourself.

To make impeller removal easier put a thin coat of SuperLube on the shaft before you put the impeller on, especially important if you're in salt.

No, you can pull the shaft w/ no problem.  Unless you have an M25 with the adapter plate that I posted about earlier.   It's the 202m-03/07 pumps (that need the female shaft to female camshaft adapter) that you can't pull the shaft.   The adapter stays in there and it's a bugger lining up the shaft when reinserting.  There may not be any C34s with that pump and adapter, no history on that.  You can get the adapter out with a magnet and then reinsert it all but you must know that trick.

Also it doesn't matter how you put the impeller in. The vanes self correct as it rotates.

K

[scgunner]

    Over the years while wrestling with that damn little circlip I often wondered how important it was to the operation of the pump, it always looked to me that is served no real purpose, of course I always played it safe and installed anyway. It's nice to know if needs be the impeller can be installed without the circlip. Ken, the reason for ziptie compression of the vanes was to make it easier to feel for the female slot when inserting to shaft.

[KWKloeber]

Mark where the shaft flat position is and reinsert it in that position.
I've not heard of an issue with the impeller not seating and needing to remove the shaft for that reason. Usually if at all, it's because it's tight on the shaft and won't come off, hence the SuperLube.
Once you figure out/correct why it's not seating, then I'd reinstall the shaft first, and then the impeller.

JTSO, everyone's mileage varies how to skin an Oberdorfer.

K

[scgunner]

    This is the first time I can remember this happening, all I can think is maybe the tolerance was slightly off. I always use lube when dealing with machined parts. The upside to this caper is I stumbled on an easier way to change the impeller.

     
           Sometimes you eat the Oberdorfer, sometimes the Oberdorfer eats you!