Impeller Change: Universal Diesel 5416

Hi All,

Wanted to say thanks, give an update on my maintenance and ask hopefully one last question.

I changed my oil and oil filter, transmission fluid, both fuel filters and bled the system. All seems good! I decided to wait on changing on the coolant until I figure a couple things out.

HERE'S MY BIG QUESTION:
I'm trying to change the impeller on my raw water pump. I have an Oberdorfer (p/n # N202M-07) raw water pump. Per the engines owner's manual, I removed the screws, front plate and the retaining ring. Using a wooden dowel to keep the shaft from coming out I was able to pull out the impeller (that took quite a lot of work). I took the impeller to the chandlery and got a new one. Pushed the new one onto the shaft and it seemed to go all the way on but there's just not enough clearance to get the retaining ring back into its little groove. Any ideas?

Yes, we compared the new impeller to the old one. It sure seems like its definitely the right replacement part (and went to a good chandlery that should definitely know). It seems like the new rubber is slightly firmer as would be expected, which makes it stick out maybe less than a millimeter more - just enough that we can't get the retaining ring back on.

Would really appreciate any help!

sailinggreg said:

Hi All,

Wanted to say thanks, give an update on my maintenance and ask hopefully one last question.

I changed my oil and oil filter, transmission fluid, both fuel filters and bled the system. All seems good! I decided to wait on changing on the coolant until I figure a couple things out.

HERE'S MY BIG QUESTION:
I'm trying to change the impeller on my raw water pump. I have an Oberdorfer (p/n # N202M-07) raw water pump. Per the engines owner's manual, I removed the screws, front plate and the retaining ring. Using a wooden dowel to keep the shaft from coming out I was able to pull out the impeller (that took quite a lot of work). I took the impeller to the chandlery and got a new one. Pushed the new one onto the shaft and it seemed to go all the way on but there's just not enough clearance to get the retaining ring back into its little groove. Any ideas?

Yes, we compared the new impeller to the old one. It sure seems like its definitely the right replacement part (and went to a good chandlery that should definitely know). It seems like the new rubber is slightly firmer as would be expected, which makes it stick out maybe less than a millimeter more - just enough that we can't get the retaining ring back on.

Would really appreciate any help!

Click to expand...

That retaining ring (circ clip) is completely unnecessary. Just leave it off. There is no where that the impeller or shaft can go with the cover on! (I've had two previous boats with this same pump and in both cases I left off the clip for years. There were no ill effects nor can there be, if you stop and think about it.)

As to why the clip was put on there in the first place: My guess would be that it's there so that when the pump is not on the engine it keeps the shaft from sliding out the backside of the pump. But it certainly cannot slide out backward when it is installed on the engine, nor can it slide out forward when the cover plate is on.

Greg - Can you put the old impeller back? If so, the new one should go. Is there a bur on the brass bushing? Did you reverse the new impeller and try it? Did you lubricate the impeller with soap?

I have a problem with your comment about stiffness; why would that make a difference?

Haven't tried putting the old impeller back on, yet. Might do that tomorrow.

There does not appear to be a front and back, just some tiny markings on one side. Otherwise both sides seem identical. But we did reverse the new impeller just to be sure and still the same problem.

Per the owner's manual, I lubricated the impeller with oil. Both the hole for the shaft and the blades.

I'm not sure what you mean by, is "there a bur on the brass bushing?"??? If you mean some little bit sticking out (from the manufacturing process), not anything noticeable.

I'd like to take back my comment about stiffness. Just that the new one looks new, as expected. You're right that shouldn't make any difference.

Any ideas???

I kind of agree with Alan's post that the retaining ring is unnecessary. But what do I know, and I'm the sort of guy would like to put it back the way it was.

sailinggreg said:

Haven't tried putting the old impeller back on, yet. Might do that tomorrow.

There does not appear to be a front and back, just some tiny markings on one side. Otherwise both sides seem identical. But we did reverse the new impeller just to be sure and still the same problem.

Per the owner's manual, I lubricated the impeller with oil. Both the hole for the shaft and the blades.

I'm not sure what you mean by, is "there a bur on the brass bushing?"??? If you mean some little bit sticking out (from the manufacturing process), not anything noticeable.

I'd like to take back my comment about stiffness. Just that the new one looks new, as expected. You're right that shouldn't make any difference.

Any ideas???

I kind of agree with Alan's post that the retaining ring is unnecessary. But what do I know, and I'm the sort of guy would like to put it back the way it was.

Click to expand...

Even with a properly fitting impeller the circlip can be tricky to get back on. But since there's no reason to put it on anyway I just never worried about it. On the other hand, if you are the sort who enjoys messing with stuff like that then far be it from me to throw cold water on anyone's fun!

I have had the same difficulty and cursed it a few times, but eventually I've gotten it back on each time. Patience and careful work with a small needle nose pairs will eventually work.
I agree that you could probably manage without it as there is nowhere for the impeller to go, but like you I prefer to do it right.
Good luck!
Frank

One thing you can do is hold the shaft out a little. Sounds easy. A magnet? Adhesive tape?

I have heard that the shaft can be removed without a problem, but I wouldn't do it on my say so.

Tom Metzger said:

One thing you can do is hold the shaft out a little. Sounds easy. A magnet? Adhesive tape?

I have heard that the shaft can be removed without a problem, but I wouldn't do it on my say so.

Click to expand...

Be careful about pulling the shaft out too far. If you pull it out from the engine, sometimes it will not go back in without unbolting the whole housing - I've made this mistake!

Given that the subject of the thread has changed, I moved those posts to a new thread.

I had always been told that it was risky to remove the raw water impeller shaft as a unit from the Oberdorfer pump housing on the engine, but after a decade of frustration with the %&&*@^% circlip, I have been doing this for several years now with no problems.

Note: I am VERY cautious when reinserting the shaft and do try to be very careful about potentially nicking the little invisible oil seal that it has to engage on its way back in. Gently and Easy Does It. It might be good to polish the shaft end edge profile with some fine emory cloth, slightly, just to help it get thru safely.

Loren

Loren Beach said:

Given that the subject of the thread has changed, I moved those posts to a new thread.

I had always been told that it was risky to remove the raw water impeller shaft as a unit from the Oberdorfer pump housing on the engine, but after a decade of frustration with the %&&*@^% circlip, I have been doing this for several years now with no problems.

Note: I am VERY cautious when reinserting the shaft and do try to be very careful about potentially nicking the little invisible oil seal that it has to engage on its way back in. Gently and Easy Does It. It might be good to polish the shaft end edge profile with some fine emory cloth, slightly, just to help it get thru safely.

Loren

Click to expand...

Loren raises a good caution here. You certainly *could* nick the oil seal and cause yourself some problems if you pull out that shaft. But seriously: there is no reason to install the circlip. None. There is no place for the impeller or shaft to go when the cover plate is on and the pump is mounted to the engine. Now, if you were to pull the entire pump off of the engine then, theoretically, the shaft might stay in the engine when you pulled the body of the pump away, but that's not likely and not a huge deal even if it did. Also, if you had the pump off the engine the shaft might slide out the back of the pump even with the cover plate on, but that's not relevant to any likely real-world situation you are going to encounter with that pump--and again, not of huge concern anyway. Or, if that really bothered you, you could always reinstall the circlip if you were planning to remove the entire pump but leave it in a drawer the rest of the time to facilitate your impeller changes.

There is nothing "wrong" with leaving the circlip off. But if someone can explain what possible harm could come from leaving it off, then I'm all ears. And I say this after a combined total of over 10 years (on two previous engines with that same pump) with many impeller changes and zero problems. (My current engine is a 1GM and it has no circlip in the first place.)