Impeller / Sea Water Pump Problem in Volvo MD2040

[hoaga]

Hello all,
I am having a bit of trouble with the seawater pump on my Volvo MD2040.

It is not pumping properly.

Some water comes through, but not the normal amount, and you also get that sound occasionally that accompanies a dry exhaust.

The impeller is not broken or cracked or worn in any fashion that I can detect.

But each of the three times I've opened it up now, one of the blades has somehow flipped backwards. Not sure how this could happen. And of course since I've detected this problem, I've been very careful to put the blades in, in the right direction.

I've noticed that there is a fair amount of scoring on the cover plate.

I've also checked the system for leaks and clogs and see none. Water sucks in easily through my strainer (by mouth pressure), and similarly I'm able to blow (by mouth pressure) out in the direction of the heat exchanger and on out into the exhaust--but it takes some pressure to move water and air in this direction.

Any thoughts? Suggestions?

Note, neither the owners manual, nor the shop manual have instructions for replacing the pump as a whole--so if anyone thinks this needs to be replaced then will I need a shop to do this?

Thanks in advance for your help.

All the best,
Arthur
s/v Morning Glory

[captain465]

You need at the very least a new cover plate. The scoring will stop the pump from drawing a suction on the intake side. This will result in a marked decrease in water flow. The cam lobe in the pump might also be worn to the point that the impeller vanes may "flip" the wrong way. If the new cover does not correct the problem, a new pump might be needed.

[hoaga]

thanks,
any idea if replacing the pump as a whole is a job I can (should?) attempt without a manual? Since there are no instructions in the owners manual or the shop manual.

thanks again,
art

[captain465]

I am not familiar with the Volvo.......but if you have a pump with a cover plate, it should be easily removeable.......usually onl 3 or 4 bolts to hold it in with a splined shaft into the engine.......no need to worry about any "timing" as with a injector pump.
Perhaps someone else on the forum can shed some more light.........

[Hudson Force]

Check to see if the center core of the impeller is spinning without the rubber portion moving with it. Sometimes these can lose their adhesion. 'all good advise above as well.

[DeepFrz]

Sometimes you can flip the cover plate over and install it outside in. Also, it isn't clear if you changed the impeller or not. If not try a new impeller.

Also not clear how you "checked the system". If I were in this situation I would remove and clean the heat exchanger and the water injection elbow at the exhaust end. Blowing air through the system by mouth will only tell you that it is not completely blocked. It wont tell you if there are restrictions in the system that are partially blocking water flow.

[highseas]

It is very common for the used impeller to appear fine but it isn't,resulting in reduced flow.The rule is to just change it anyway.