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ralphmacey 11-15-2007 05:06 PM

impeller change
I have a Univeral diesel M3 20B and I would like to change the impeller. There is a cover over the impeller held by three bolts however the manual says you have to remove the waterpump from the engine before taking off the cover. Has anyone any experience with this engine?

Pub911 11-15-2007 10:34 PM

I have an m4-30 and have been able to answer similar questions by searching a competing marine supplier site where extensive exploded diagrams are viewable online. Search the manufacuter name and you'll find it.

Gene T 11-16-2007 03:03 PM

You read the manual?

Sorry, no help on that engine but insanely stupid if it is necessary to remove the pump first. Maybe there is another reason, like the need to grease an o-ring?

Rockter 11-16-2007 07:22 PM

Yes, insane. In a rush, you won't have time. take the cover off and have a wee look.

deniseO30 11-16-2007 08:00 PM

3 bolts... thats a sherwood pump, I think! Err don't forget to close the intake valve! Is it down low on the port side? I think you may find it easier to remove it then change the impeller down low where it is. I have a 5416 but the pump is up above the engine water pump. Featherman is a good source I found online

bestfriend 11-16-2007 09:02 PM

You can do it by just taking off the housing cover. There is no reason to take the whole pump off. Get a new gasket too. There is only a shaft between the pump and the block. Make sure you mark the hoses so that you put them on right (if you take them off) and get the impeller turned in the right direction. Also, lube the impeller so that it doesn't stick the first time you start it. You can use dish soap.

Here is the cover:

Here is the impeller in the cover:

Here is the rest of the pump, you can see the shaft that sticks into the impeller on top and the shaft for the block on the bottom.

ralphmacey 11-16-2007 09:07 PM

Do I just pry the impeller out with screwdrivers of needlenose pliers?

bestfriend 11-16-2007 09:10 PM

Yes, it should come out pretty easily. Once you take it off the shaft, it is just sitting in the cover, nothing holding it there but old age. Why are you changing the impeller? You should know that if there is any weepage of oil/grease out of the pump (you can see it in the third photo) or water out of the cover(from the little screw in the first picture on the bottom of the cover) You will need a new or rebuilt pump.

ralphmacey 11-16-2007 09:13 PM

Thanks so much, I'll give it a try.

sailingdog 11-16-2007 09:16 PM

Just don't scratch the surfaces, since that will cause the new impeller to wear.

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