Yanmar 2QM20 impellers ...

[partingclouds]

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.

[sailormed]

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 “wrong” direction.

[partingclouds]

Thank you, sailormed. So then, it doesn't really matter as there is no "wrong" direction, right?

[Compass790]

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

[a64pilot]

Any lube you use is gone in a few seconds. I’ve found that dishwashing soap works well too as I don’t want to have to stock glycerine.
I do think it’s best to have something to keep it from being a dry start.

[Compass790]

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