What am I doing wrong? New impeller not working

Stu Jackson · Aug 3, 2015

I read this late last night (too late to help you) and reserved a reply until this morning. I wanted to see how many more times you'd try the old one, first. Geez, what different result did you anticipate?

The single faced Oberdorfer faceplates obviously can't be turned around. If this happened to me, I'd, first, sand the faceplate and that should work, it always reportedly has; then buy a second new impeller so you're not tempted to keep the old one and confuse it with a new one.

You don't mention going through gaskets...

I think sometime earlier I sent you a link to our C34 tech wiki on engines.

This is from that:

http://www.c34.org/wiki/index.php?title=Raw_Water_Pump_Priming_Problem

Have you ever smoothed out the ridges worn into the inside of that faceplate?

For others with M25 series engines:

Engines 101 - The BIGGEST & BEST collection of M25 Series Universal Engine Information on the Internet, plus some M35, too

http://www.c34.org/wiki/index.php?title=Diesel_Engine

Ralph Johnstone · Aug 3, 2015

Re: What am I doing wrong? New impeller not working

jonelli said:
I'm going with the theory that the seals inside due to the cover plate are a likely culprit, and the old impeller is just softer and worn into the groove which is why it works okay.

I'll let you know in a couple days.

That's about the only illogical suggestion that may explain why the old impeller works so well as opposed to the new one.

Don't leave us hanging here as this is one of those problems that really keeps me awake at night

!

hvbaker · Aug 5, 2015

jonelli said:
STU nailed it. Resurfaced the inside of the cover plate smooth, and all is good in the world again with the new impeller. Here's what I did for those that are curious. Do not take what I did as the correct method. I will never claim that I know what I'm doing, I will just try stuff that seems like it might work and hope I get lucky. I brought my orbital sander to the boat with a medium grit sand paper on it. I put the plate with the inside grooved part facing up on a rug (for some friction), pressed the sander down on it and let the orbital do the work until the groove was smooth. Then I took a 220 grit sand paper sheet on my formica counter top and slid the plate back and forth on that until I could see scoring marks on the entire surface (the orbital tends to take more off around the edges leaving the center a little higher, but I needed to take a lot of surface off and that was the easiest. Then, the counter top sand was to flatten the piece as flat as I could make it. Then I used 600 grit on the counter top and polished it to get rid of the 220 scoring marks. Attached is the plate BEFORE I sanded it. You can see the groove is pretty deep. I installed the new impeller with some soapy water on it, then put on the cover plate and gasket, made sure it didn't leak (found a new problem though, will explain in a sec), started the engine and voila! flowing exhaust raw water again. Yay! The resurfaced cover plate does not leak, but while inspecting that nothing is leaking I discovered something leaking where the pump attaches to the block, and it looks like it may have been leaking before. I'll start a new thread. @Stu - Thanks for all the links. I just didn't read them all months ago or if I did, I didn't retain all the info. There's a lot of good info there.

Bummer after all that the seal in the pump is leaking and you need a new pump or rebuild.

Capt jgw · Aug 5, 2015

I can't see how the C clip has any purpose. The shaft can't slide into the engine far enough to disengage the impeller (at least on my engine, I suppose it could on some, and that pump can be mounted on many different models). The clip does nothing to prevent the shaft sliding out and rubbing on the cover plate, which I would be more concerned about.
IMO it just makes it harder to get the impeller out, and on some applications if the shaft pulls out at all you have to remove the whole pump to get it back in. I'm not running mine with the clip in and I don't have any problems with it.

Ron20324 · Aug 5, 2015

When you take the cover off after run-or-no-run, are the impeller vanes in the same directions? They should be as soon as the engine turns over. If the impeller had a brass hub, might the rubber be coming loose when rotaing at speed? That's not uncommon.

Ron20324 · Aug 5, 2015

An idea came to me, maybe a money-maker... How about Lexan covers so you can see the impeller while it is running? Even in this case, a temporary clear cover would allow visual insecection while the engine is running.

Capt jgw · Aug 5, 2015

That's not too bad a job. Moyer Marine has the seal kit. Getting the old seals out can be a PITA, but the new ones go in easy.

JamesG161 · Aug 5, 2015

Just for the record this type of pump is....

1) Flex vane positive displacement rotary pump
2) It is self priming...but only at short suction distances.
3) Flow is proportional to the rpm of shaft. Flow up as rpm up.
4) The impeller must seal against the shaft side plate and the cover plate or bypassing will occur which renders it useless.
5) The paper thin gasket allow the cover plate to come in contact with the outside edge of each vane.
6) There is a thin raised edge on each vane , from hub to tip. They acts like an O ring fiction seal against the two plates.
7) More vanes... more flow.
8) Low pressure discharge, my guess on this unit is less the 3 psi.

You resolved the plate contact issue which caused the bypassing of the vanes.
Jim...

PS: This pump does NOT convert to a centrifugal pump at high speeds.

OS2Dude · Aug 7, 2015

Only guess I've not seen here is to make sure the direction the arms bend in is correct. When we got our 1985 C30 with an M-25, the impeller was slightly too big and the arms actually bent towards each other, every other pair. Even when we took it out and put it back the right way it went back to the opposing arm position.

I'd love to hear if you resolved this and if you could determine what was wrong.

Stu Jackson · Aug 7, 2015

jonelli said:
@Stu,
So is that stupid clip ring really necessary? I saw the posts about it being just to hold the shaft during shipping and it not being functional, but has anybody run it without the clip ring for long periods and been okay? I rally hate that ring. And I bought a spare one for something ridiculous like $8.

It seems to me that the shaft might be able to move around or slide back and forth a little without the clip, that there's literally some wiggle room. And I'm thinking that it might not be the best thing to have it free to move like that.

I don't know. Take it off, try it without it and see what happens.

I have no idea why people grouse so much about that clip. I get mine on and off with a small flat bladed screwdriver. They make circlip tools to make ti easier. Buy one and you can stop grousing about the clip.

JamesG161 · Aug 7, 2015

The shaft lip seals are now leaking, so the whole pump needs to come off now and get serviced.

Sometimes you can use a flat blade screwdriver to gently tap the lip seal in a circle and reseat the O-Ring. Rebuilding is best, but you will probably need the cover plate also, eventually. I looked at rebuild kit for mine ~$120 (everything except housing ), but a completely new pump was ~$190. I picked the new pump, since the pump back plate IS the housing and it wears too.

@Ron20324

An idea came to me, maybe a money-maker... How about Lexan covers so you can see the impeller while it is running? Even in this case, a temporary clear cover would allow visual insecection while the engine is running.

Good idea but look up polycarbonate instead of Lexan.

http://www.professionalplastics.com...t/downloads/PolycarbonateGP_DataSheet2015.pdf

Your plastic must not deform, flex or etch if pump runs dry, but Lexan might work as a test.

Jim...

PS

olycarbonate is jet fighter cockpit windows.

Stu Jackson · Aug 7, 2015

If you go back to the C34 engine links I've been sending you, you'll find out how to rebuild one, with pictures.

Jongleur · Aug 7, 2015

I have no idea why people grouse so much about that clip. I get mine on and off with a small flat bladed screwdriver. They make circlip tools to make ti easier. Buy one and you can stop grousing about the clip.

I had a dilly of a time trying to get that
ring back on, so I went and bought one of
those tools $25 (ouch). Made it only a tad
bit easier. Then I find out the ring doesn't
need to be there. WHAT??? Ah, well...

ArkadiyS · Nov 4, 2015

Jonelli, did you get your problem resolved? I was just looking through the forums and stumbled on yours. We had the same problem on our M25. Old impeller was pushing water out, while the new one was not. 2 things: 1 - new paper gaskets are thicker than the original ones, so you would need to apply a lot of KY gel to it to make it as air tight as possible; 2 - make sure that the pump cover is as clean and smooth as possible. I have also used a hand pump to blow the hoses, all the way to the water muffler until i saw water coming out of the exhaust and back the other way, until i heard/saw bubbles outside (through an open seacock. Based on what our mechanic said, is that a little difference in pressure (when you suck in some air) could make all of the difference, so clear the lines as well as you can. This damn problem has really stumped me for a while as well. One thing to also tell you is that even with the water flowing out and a new impeller in-place, the amount of water coming out is not what it used to be with the old impeller?? I am still fuzzy on that one, but the engine is working well in the 160 - 180 degrees, as it should. Weird, but it did work!

JamesG161 · Nov 4, 2015

If you put a "thicker" gasket than spec, you will bypass along side of the impeller. The cover plate presses and seals the pump impeller. One reason it must be resurfaced/replace as it wears as it seals.
Jim...

What am I doing wrong? New impeller not working

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