Sea Water Impeller Directionality..does it really matter??

[Crownin' Around]

OK.. I have searched the forum and have found differing schools of thought on this topic. Some say do not worry about the direction of the impeller vanes when installing as they will self orient others say no you have to put them in the direction they spin form the get go.

I have a Volvo 4.3L GL (1999) with the raw water pump mounted off the crankshaft. Does it matter how I orient the vanes when installing the new impeller?

If it does...what direction should they go? I would assume the same direction as the crank spins....looking at the motor from the front that would be clockwise correct?

by the way my Seloc manual makes no distinction nor does any Volvo literature I have found....

I tend to think I am over thinking this, but would like some reassurance from some peeps who have changed an impeller a time or two!

Thanks!

 

[redjmp]

Re: Sea Water Impeller Directionality..does it really matter??

Doesn't matter, they will self correct as soon as you fire up the motor.
At higher rpms the vanes don't even touch the housing.
The impeller is offset in the housing so that during half the revolution the vanes on one side barely make contact at all and will self correct due to the resistance of the water.

 

[picklenjim]

Re: Sea Water Impeller Directionality..does it really matter??

Yep, redjmp is correct. I bench tested this one time with the end cover off so I could watch and intentionaly had the vanes going the wrong direction. In one revolution they were all corrected. Tip, you may want to put some liquid dish soap all over the new impeller to aid in the intial dry start.

 

[muc]

Re: Sea Water Impeller Directionality..does it really matter??

Most will self correct. Some don't.
But my question is ---- why put it in backwards when its just as easy to put it in right?
Good Luck Muc

 

[JustJason]

Re: Sea Water Impeller Directionality..does it really matter??

There are 2 types of water pumps. There are high pressure pumps, and there are high volume pumps.
Hi volume pumps have longer, more flexible vanes, and will usually self correct....... usually.
Hi pressure pumps have shorter, stiffer vanes, and will no self correct. They will sit there and spin until they are burn't out.

So like Muc says... Why put it in backwards?

It takes all of 2 extra seconds to put it in correctly.

 

[Don S]

Re: Sea Water Impeller Directionality..does it really matter??

There are high pressure pumps, and there are high volume pumps.
Hi volume pumps have longer, more flexible vanes, and will usually self correct....... usually.
Hi pressure pumps have shorter, stiffer vanes, and will no self correct. They will sit there and spin until they are burn't out.

You have that backwards Jason, the longer vanes will not flip over, that is why there was a bulletin on the Alpha I Gen II drives (with the longer vanes) about installing them correctly.

 

[Brentathon]

Re: Sea Water Impeller Directionality..does it really matter??

Also, redjmp is wrong.....some impeller vanes (i.e. Alpha) MUST continue to contact the casing (or "housing") throughout the revolution, or they won't provide enough flow/head. I had an issue with a defective impeller that had stiff vanes, and at high rpm's they weren't straightening out fast enough to maintain contact, and therefore not pumping enough.............sent it back to Sierra, and they even stated the same thing.

 

[Crownin' Around]

Re: Sea Water Impeller Directionality..does it really matter??

Most will self correct. Some don't.
But my question is ---- why put it in backwards when its just as easy to put it in right?
Good Luck Muc

I agree with your statement. I would like to put it in correctly from the beginning.

....so correctly is with the vanes bent in a manner following (trailing) the direction of the crank (in my case) correct?

Thanks all for the replies. This forum is a valuable resource!

 

[redjmp]

Re: Sea Water Impeller Directionality..does it really matter??

Also, redjmp is wrong.....some impeller vanes (i.e. Alpha) MUST continue to contact the casing (or "housing") throughout the revolution, or they won't provide enough flow/head. I had an issue with a defective impeller that had stiff vanes, and at high rpm's they weren't straightening out fast enough to maintain contact, and therefore not pumping enough.............sent it back to Sierra, and they even stated the same thing.

I stand corrected! Learn something new everyday. That why I love iBoats!

 

[Brentathon]

Re: Sea Water Impeller Directionality..does it really matter??

I probably should have been more courteous to you, redjmp.

And all of the flexible vane impeller pumps (with offset shafts) that I've come across, have the impeller vane tips bent in a manner where they're "trailing".

 

[redjmp]

Re: Sea Water Impeller Directionality..does it really matter??

I probably should have been more courteous to you, redjmp.

And all of the flexible vane impeller pumps (with offset shafts) that I've come across, have the impeller vane tips bent in a manner where they're "trailing".

No offence taken but the diagram you posted is offset pretty much the same as all the pumps on every merc, johnrude, or mercruiser lower unit I have ever worked on and none of them seemed to care which direction they were installed in as they would self correct. That impeller does seem to have thicker vanes on it though and the housing suggests it is not the type of housing found in a leg.

 

[Don S]

Re: Sea Water Impeller Directionality..does it really matter??

I think his drawing was to show how the vanes open and close (bend and straighten out) while turning more than showing a particular type of pump.

 

[Brentathon]

Re: Sea Water Impeller Directionality..does it really matter??

Yep, the pic was simply to answer the OP's question:
"....so correctly is with the vanes bent in a manner following (trailing) the direction of the crank (in my case) correct?"
The pic shows a different port arrangement, as in most marine pumps.

I also believe that most of these marine pumps would self correct, but I would recommend installing them correctly............I wouldn't want to take a chance with something so critical, as the impeller of a cooling pump.

 

[Crownin' Around]

Re: Sea Water Impeller Directionality..does it really matter??

Thanks Gents for your help!