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Old 10-04-2019, 07:44   #1
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Yanmar 2QM20 impellers ...

Both spin in the same direction, counterclockwise, right? I had a mechanic install both, and now am replacing those he put in. The one in the water pump">raw water pump looks like it was installed backwards, the lobes being bent to the left, effectively being pushed on their axis rather than pulled. As it is, it just looks like trouble, but my question is, does it really matter? It was pumping like this, but I wonder if it would pump more water if the lobes were installed the other way. ??

Thanks for any insight.
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Old 10-04-2019, 08:00   #2
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Re: Yanmar 2QM20 impellers ...

When you stop the engine the crankshaft often finishes with a partial rotation against its normal rotational direction because of compression. This is the reason you often see one or more vanes of the impeller in the ďwrongĒ direction.
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Old 10-04-2019, 08:42   #3
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Re: Yanmar 2QM20 impellers ...

Thank you, sailormed. So then, it doesn't really matter as there is no "wrong" direction, right?
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Old 10-04-2019, 14:11   #4
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Re: Yanmar 2QM20 impellers ...

No it doesn't matter, they instantly flip over but I'd install them in the normal direction of rotation. Dont forget to use the lube they supplied or if they supplied none silicone grease or glycerine works good
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Old 11-04-2019, 03:43   #5
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Re: Yanmar 2QM20 impellers ...

Any lube you use is gone in a few seconds. Iíve found that dishwashing soap works well too as I donít want to have to stock glycerine.
I do think itís best to have something to keep it from being a dry start.
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Old 11-04-2019, 12:56   #6
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Re: Yanmar 2QM20 impellers ...

I thought the 2qm20 was raw water cooled. Has yours had a fresh water conversion done?
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