Impeller Replacement: Which Direction do the Fins Point?

[blue...@gmail.com]

I'm replacing the raw water pump impeller.  Should the new impeller fins face forward (clockwise) like they would be scooping water, or backwards (counter-clockwise) as though they were pushing water?  The old impeller was in pieces so I can't use it as a guide.

I think I saw "clockwise" in one of my service manuals, but I am hoping someone has the answer and I won't have to go on a tedious search through  multiple manuals. This is a Westerbeke 38B 4 diesel.

Yes, I know I have to make sure I have found all the old impeller pieces.

Thanks,

Barry Clark

Swan's Wing  NS354, #71

Urbanna, VA

[Joe Valinoti]

Barry:  I used to worry about that but read somewhere it will sort itself out once the engine starts.  There may be articles about that on the web.  The other alternative is to crank the engine and see which way the shaft turns.

 

Joe Valinoti
S/V iL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA

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[W C]

Yes, I have read that it will sort itself out too, but wouldn't it be better to have everything going in the right direction at the beginning if you could?  Still, knowing which way the shaft turns doesn't really help.  Should the fins point in the direction of the rotation or the other way?  That's the question.  I suppose I could just contact Westerbeke, but that's too easy.  LOL

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[Mariner's Cat V 26C Brentwood Bay BC]

Take a picture of the old one before you remove it

[Tim in STL]

Try this link:      https://marinehowto.com/changing-a-raw-water-pump-impeller/

Tim in STL

White O’morn NS26U

Harbor Point Yacht Club

West Alton, MO

[W C]

Good link, thanks.

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[W C]

I decided that the best source to answer this question was to ask Westerbeke.  They replied this morning: 

Thank you for your inquiry. It does no[t] matter which direction you have the impeller blades facing on installation, they will find the correct shape/direction as soon as the engine and pump starts turning.

End of mystery.

Barry Clark

Swan's Wing NS354, #71

Urbanna, VA

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[Bob Illingworth]

Just one further observation, sometimes when diesel engines are stopped they can rotate backwards a quarter turn or so, this would be enough to reverse the impeller blades in the water pump until the engine is started again.

 

Bob Illingworth

Nonsuch Luck 30U #367 (GBR1262T)

Moored Brightlingsea, UK cruising the rivers of East Anglia and the North Sea.

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