Oberdorfer Impeller

[WBurgner]

I recently tried to install a new impeller for the Oberdorfer raw water pump on my Universal M40. While it looked identical to the one removed it did not leave enough room on the shaft to allow replacement of the split ring.

When asked, Torresen Marine said they had not heard of that problem before, but that the split ring was not really necessary since niether the shaft nor the impeller were going any where once the cover was in place.

Sure seems like the designer must have had a good reason to use the split ring, but not having it will sure make the changing of an impeller easier especially if speed was important.

Has anyone run into this? Any thoughts on extended use without the split ring holding the impeller in place on the shaft?

Bill Burgner
E381 #515

 

[tenders]

I have an Atomic Four with a nearly identical pump.

I could be wrong but I think there is a bit of fore-and-aft play without the clip. The impeller fits pretty tightly into the chamber fore-and-aft and the clip anchors the shaft to that fairly tight specification.

I don't see how it would be possible to cut the slot on the engine side of the shaft to match every engine to perfect tolerance, which makes me suspect those slots are cut a little deeper than necessary. Over time (or maybe over not so much time...?) without the clip the resulting wobble can wear the inside of the cover plate and/or cause the seals to leak.

 

[hodo]

Impeller

The shaft floats a bit on the Oberdorfer pump, and if you dont hold it out while installing the impeller, it will push in enough to not allow the snap ring to be installed. I use a strong pencil type magnet to hold it out while working the impeller on. Once the impeller is in place a bit of side pressure on the imperr with your finger should keep it from sliding while you install the snap ring.Do not pull it out too far as you will have to remove the pump to get the shaft re aligned with the drive. Good Luck, Harold

 

[WBurgner]

Impeller

Thanks Harold. I just got an email from another person at Torresen who said it was easier to install the impeller and ring if the shaft is removed. Your comment about the difficulties encountered if you remove the shaft echoes advice I had received a few years ago when I first aqired the boat. Worrying about letting the shaft out to far caused me to press the shaft inward firmly while removing the old impeller. I will try pulling it out slightly to expose the slot and install the ring.

They sure make it confusing and I am lucky not to be tryng this in a seaway.

Bill

 

[Loren Beach]

We routinely remove the shaft for impeller replacement on our '88 M25XP with the Oberdorfer pump. It has a flat milled onto the inner shaft end and I just rotate until it slides on in. That little snap ring is a real bear to install, for sure.

Loren

 

[Geoff Johnson]

We routinely remove the shaft for impeller replacement on our '88 M25XP with the Oberdorfer pump. It has a flat milled onto the inner shaft end and I just rotate until it slides on in. That little snap ring is a real bear to install, for sure.

Loren

I understand the concern to be that pulling the shaft will damage the oil and water seals, but I find I can't replace the impeller without pulling the shaft. A few years ago I replaced the shaft because the seals had worn it to the point that water was dripping. I now keep the old shaft with an impeller on it so that I can pop it in in case of an impeller failure, thus avoiding the hassle of fitting that pesky clip ring on the shaft when the boat is rocking around. With a SpeedSeal cover and a spare shaft, changing the impeller is like an Indy pit stop:clap:

 

[WBurgner]

Spare Shaft

The idea of keeping a spare shaft with the impeller mounted sounds like a very good idea, I think I wil lgive that a try. I have a tendency to distort the ring in the process of removing or replacing the damned thing, so have the opportunity to do it with ample time is attractive. I wil lhave to come up with a good way to store it without distorting the vanes. Any one found a source of the rings at a price lower than $8 - $9 at Torresen or Moyer?

 

[footrope]

Oberdorfer pumps

I bought a plier type ring tool to help avoid the distortion problem when removing or installing the ring. It works pretty well. Do you drape something over the front of the engine when working on the pump? I sometimes drop tools or parts into the engine bilge and then that magnet on a stick comes in handy.

I discovered that the ring can be installed even with the shaft fully pushed in when using the plier tool. It takes a bit of pressure but I was able to do it this last time, even though it didn't look like it would go. It is frustrating trying to figure out how to keep from pushing the shaft in too far.

 

[tenders]

Sears sells "snap ring pliers." Silly-looking tools...until you need one.

 

[Shadowfax]

Snap ring pliers are a must for this job. It's like a $15 or $20 tool and generally comes with different size ends and different angled ends. As necessary as a Cresent Wrench in the tool box to me

 

[Gary G]

Sherwood pump E28+

I have a 1983 E28+ with A Universal M15 (5411) modified from its original sea water cooling only design to use a closed cooling system and heat exchanger (done at the factory I think). Anyway, I had to replace a beat upimpeller in the seawater (Sherwood) pump recently and in the process I had to pull the shaft quite far out to get the new impeller on and that pesky snap ring in place. Through wiggling it around I was able to get the shaft fully inserted into the pump and place the cover back on. Everythings seems fine. I have not started the engine yet. Can anyone assure me that there is only one way to insert the shaft and that it's ok to run the engine? The user manual states that if the shaft is pulled out then the pump must be disassembled to make things right. I'm paranoid that I'll grind up pump seals or bearings or something unless I pull this thing apart. Is that really necessary??

Gary

 

[tenders]

Does the manual really say that without giving a reason? I think the worst that could happen would be that the shaft slot might, but not necessarily, nick the seal a little bit while being removed and reinstalled.

I wouldn't hesitate to start 'er up. If she grinds or spurts, turn her off. If she leaks, the seals probably needed to be replaced soon anyway.

(The shaft slot looks like the slot in an extremely large panhead (flathead) screw. If the pump was assembled correctly, it doesn't matter which side it engages.)

 

[footrope]

My impression of the caution about pulling the shaft out too far is that the device (adapter) that receives the impeller shaft is designed to "float" into alignment between the engine and pump body while the engine is running. It could become misaligned if it moves while the impeller shaft is pulled all the way out. The instructions to correct the condition describe a procedure that includes tightening the pump body WITH THE ENGINE RUNNING (be careful of the moving v-belts). Hot bearings in the pump are apparently a symptom of misalignment.

I make sure the shaft doesn't turn - it wiggles a little - after pushing it fully in and haven't noticed a problem. I think some crud holds that adapter in place back there. I try not to pull the shaft out at all, but it usually comes out a little.

The procedure also talks about the bearing grease cup, which is a feature of my Oberdorfer model. It's one of those things I give a quarter turn every time I check the belts. When it's empty - all the way in - I remove it and refill with a good general purpose grease and reinstall.

I don't understand how there could be a problem if the adapter doesn't move enough to prevent the shaft from being re-inserted into it, assuming the procedure to align everything was followed the last time the pump body was installed. I have not had the pump off the engine to see just what is in there and test this hypothesis. (that's my disclaimer! IOW - YMMV)

The Specs and Docs section of this website is a great resource if you did not receive all the manuals with your boat.

 

[WBurgner]

Pulled Shaft

Well I pulled the shaft a little to try to get the ring in place and managed to get into the situation the manual cautioned against. Had to remove the whole pump to get the shaft re-engaged. While it was not difficult it took plenty of time and I would rather not have to do it each time the impeller needs to be swapped out. On a positive note it was a great learning experience. There are so many...

Bill
SV Totem
Orlando

 

[pvajko]

How do you know you pulled the shaft too far out?

For the first time (I bought the boat last year) I checked the impeller and pulled it off the shaft. I knew I had to hold the shaft in place, but I was not very good at that so it may have moved it about a half inch or so.

How can I tell if it was too much and I have to remove and reinstall the pump? Let's say I just put the new impeller on, start the engine, what are the symptoms if it was pulled too far out?

 

[Stu Jackson]

This includes a picture of an Oberdorfer shaft and impeller:

http://c34.org/bbs/index.php/topic,6766.0.html

If you have a MALE end on your shaft (as pictured), you can easily remove and reinsert the shaft. If you have the older female shaft end, it would be wise to leave it in and have to resort to replacing impellers with the shaft inside, otherwise you do have to remove the pump.

I've run the impellers without the snap ring, but mostly do use them. I don't have the special tool, but use two very small drivers.

Removing the shaft will NOT harm the seals. The shaft slides in through them and rests on the carbon bushing anyway.

These things CAN be rebuilt, rather than buying new. Heck, if I can do it...

 

[pvajko]

???

If you have a MALE end on your shaft (as pictured)

Thanks Stu, the only problem is that I haven't pulled it out yet so I don't know if it is a male end or not (on the drawing in them manual it looks like it's the female). It just moved a little bit out, about half an inch then I pushed it back.

What confuses me is the manual saying that "If the shaft does come forward during the changing of the impeller, it will be necessary to remove the complete pump."

So, what does it mean forward? How far? 1/8"? 2 inches? And how can I make sure it did not come forward too much? Is there any way to check?

And I don't understand what would I break by moving the shaft forward that can only be fixed by the removal of the complete pump.

 

[Stu Jackson]

You're absolutely right.

Things is I don't know your engine's age. Mine's a 1986 and I had exactly the same manual and instructions, but started peeking around the Torreson website and found out about the two different shaft ends.

Thinking as you do: "What the heck, if it doesn't work I gotta pull the pump anyway" approach, I pulled it and it was a male end. If it's not, whaddya got to lose if you have to pull the pump anyway. I have a photo of the INSIDE female fitting that I still have to download from my camera. I post it on the C34 rebuild article I linked to before.

Basic conclusion: Go for it.

 

[Frank Langer]

I have replaced the impeller several times, and it really isn't so very complicated. If the shaft comes forward (about 1/2 to 1 inch) it will eventually come out of the slot at the back of the pump. If it does, it will often slide right back in--you can easily tell if it's back in place, if the cover will fit on; if the shaft isn't in the slot, the cover will not fit on the front of the pump as the shaft sticks out.

If you can't slide the shaft back in easily (a flashlight shone into the pump will show where the slot is), you have to undo the several bolts that hold the pump to the engine--easy, as long as they are not corroded in place. Once you have the pump off, you can easily reinsert the shaft and remount the pump. Put the cover on and complete the install, except keep the bolts holding the pump to the engine loose--ie. only slightly hand tight. Start the engine, let it run briefly to allow the pump to align itself, then tighten the pump mounting bolts.

I'm no mechanic, and cannot take responsibility for the veracity of this information, but it has worked well for me.

Frank

 

[pvajko]

I decided the shaft did not come forward too much and just installed the new impeller, I'll see what happens when the boat is in the water and I start the engine.

But I really had a hard time reinstalling the snap ring, I have no idea how this can be done on the water in an emergency situation.