Water pump that won't pump

[egmonster]

Stumped and need some help here.

I just changed the impeller on my oberdorfer water pump and now the pump will not work.

I have check the system for obstructions and everything is clear. I tried priming by adding water at the strainer and it pumps down but very slowly.

The pump will not draw through the strainer.

System was running fine before changing the impeller which was two years old and not broken or damaged when removed.

thanks

[ILikeRust]

Check the thickness (width) of the new impeller as compared to the old. If the newer impeller is even just slightly narrower, it will not make the contact with the sides of the pump cavity necessary to draw. I.e., the water will be able to just squoosh past the sides of the vanes.

Another thing to check for is wear on the removable back plate. The plate can wear so that there is space between it and the side of the impeller.

[Mo]

Absolutely check as Bill suggested. Did you have the inlet valve raw water valve shut off and did you turn it back on. Have a good look at the valve and ensure it's functioning properly.

[roadnsky]

You might wanna read this thread too...

http://www.moyermarine.com/forums/sh...impeller+small

[ndutton]

Here's what the guys are talking about

I had exactly this situation AND a worn pump cavity (determined by depth measurement compared to Oberdorfer specs). The combination of the two resulted in the same symptom as the topic of this thread. I changed the impeller and no joy.

Being a cheap S.O.B. I opted for Don's suggestion of 'facing' the pump where the cover plate attaches. If considering this be advised it takes a steady hand to keep the surface flat. The gasket is paper thin and will not compensate for an uneven surface. Permatex #2 will then be your friend.

On the other hand, where's the risk? Your pump doesn't work now. I'd suggest making careful cavity depth measurements before deciding on a strategy.

[marthur]

On the other hand, where's the risk? Your pump doesn't work now.

Niel is right on the money with this. If this is the problem, I might go for it as well. I always look at the cost of my alternatives. If I have to replace the pump anyway, I might as well try fixing it. Even though it doesn't always work out, you are ahead in the long run.

I can think of only one reason to hold off: if you commit to buying a new pump and can re-install the old impeller, you would have a working spare.

[olebiker]

Maybe check the cam shoe as well. It could be a small part of the problem.

[egmonster]

thanks everyone for the great information, but no joy at this point.

1. Thru hull confirmed open at all times with no in-line blockage.

2. Purchased my replacement impellers from MME and assumed they would be good, but confirmed anyway that they meet specs and perfectly match the old impeller.

3. There does not appear to be any spacing issue within the pump as minor compression on the impeller can be felt when replacing the back plate.


I still have to check the cam but won't get back to the boat for several weeks.

[Administrator]

System was running fine before changing the impeller which was two years old and not broken or damaged when removed.

Put the old impeller back in, and see what happens?

Bill

[JOHN COOKSON]

Originally Posted by egmonster

Stumped and need some help here.
I have check the system for obstructions and everything is clear. I tried priming by adding water at the strainer and it pumps down but very slowly.
The pump will not draw through the strainer.

Did you check to see if the outlet is blocked?

TRUE GRIT

[Ajax]

Did you position the impeller vanes in the correct orientation?

[joe_db]

Last time my pump didn't work a small fish was stuck in it!

[romantic comedy]

The impeller will just flip to the correct orientation.

[Bob N]

I know they are SUPPOSED to filp the right way, but I had the same problem this afternoon. Maybe they don't always flop over. The freshwater system was working fine when I hauled the boat in November. Today I changed the impeller and started it up on the hard (inlet hose in a five gallon bucket of water). No water was drawn out of the bucket. I am going to check the vane orientation. Fortunately, the old impeller looks like it was in fine shape, so I'll also try putting it back in. (As Don always says, if you've made a change, suspect that you did something wrong.)

[JOHN COOKSON]

Bob N.
A couple of ideas:
Did you prime the pump?
Is the intake resevoir as high or higher than the water pump?

TRUE GRIT

[Bob N]

First, I was referring to the seawater pump on my FWC engine.

Now: I was following the same procedure I follow each spring for starting the engine before the engine is launched. The strainer body filled with water and there was water in the pump when I opened it up to see what was going on. There was just enough water on the ground below the boat to suggest that some small amount went through the exhaust system.

I'm thinking I will try opening up the strainer and inject some water with a squeeze bulb to see if some extra priming will help.

I'll also check to see if the impeller is thinner than the old one, as folks have suggested above. But the new one is one that I just bought from Don.

[grant.mckenzie]

If you are using rubber gasket might want to make sure that it is seated properly and nut jamming the impeller. Happened to me yesterday.

[Bob N]

I swapped out the new impeller for the old. The new one measured 1/64" undersize. The pump is now pumping like a champ. Of course, now I am worrying about the engine coolant pump, which I also put a new impeller in. I'll have to crawl down into the bilge to check that out if the engine runs hot after launching.

[sastanley]

Bob N/egmonster...

It would appear from this thread that you have two different accounts...please confirm you are the same person so we are satisfied that your issue is solved...

We've gone very far down the impeller rabbit-hole previously so we like to confirm things from time-to-time!

[Bob N]

It's just plain old me--Bob N.

[Bob N]

Who/what is "egmonster?" I'm just "Bob N," always have been.

[ILikeRust]

This thread was started by someone with the user name "egmonster." Partway through the thread, Bob N said, "Hey, I have the same problem." Then a few posts later, Bob N reported "Hey, problem solved."

So for the casual thread-reader, it looked like egmonster suddenly started posting as Bob N partway through...

[ILikeRust]

It looks like egmonster hasn't checked in here since his last post upthread here.

[roadnsky]

Originally Posted by ILikeRust

It looks like egmonster hasn't checked in here since his last post upthread here.

I concur Doctor...

[prstack7]

With the advice of the forum on this thread and others and the advice of
Don by email, I now understand the problem with new impellers in old pumps. The PO of my boat never changed the impeller. When I did, I experienced a lack of water flow. I switched back to old impeller and had great flow. I removed the cover plate and discovered deep grooves. I sanded down the plate, soaked the new impeller in MMO for 2+ days, reinstalled new impeller, and the system works great. I have a slight drip from the plate because I didn't sand completely flat, but it's very slight.