Impeller - Blades which way?

Richard10002

Richard10002

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About to fit a new impeller, looked at the photo I took of the old impeller in situ, and some of the blades are compressed one way, and some the other so, having done the right thing, I'm none the wiser.

Googled for pics and advice and, whilst I could not find anything specific, it seems that it may not matter as the blades sort themselves out - as per Flossdogs advice this afternoon. I'm still a bit wary so any ideas as to which way they will end up compressed.

The intake of my pump is top left and the outlet is top right. Is the water taken the short distance from inlet to outlet, (where the cam compresses the blades), or is it taken the long distance, (where the blades stretch to full length before being compressed again).

Volvo Penta MD22L if that helps

Hope this makes sense

Many Thanks

Richard
 
Now impellor blades will all be straight out from the hub, twist it in the direction of rotation as you put it in to get blades the right way, they will sort themselves anyway when you turn the engine over.
Old impellors are a bit more picky about going back the same way as they came out as the blades are stressed.
 
Doesnt really matter.If the blades are leaning one way, leave for a few days and they will almost straighten themselves again,if you get the lean the wrong way as soon as you turn the engine over they will go the right way. Used to try and get them the right way but over the last 20yrs havent bothered and had no probs.I always put some silicon grease on them,then if the water is a bit slow coming thro. you wont knacker the impeller.
 
Just put it back the easiest way you can. It'll sort itself out once it's rotated. And a smear of silicon grease will cut out any wear before the water comes through. It's also useful stuff to help self priming when the pump gets a bit worn.

Not that it particularly matters, if you turn the engine over before you replace the cover on the pump, you'll see how the blades like to line up when it stops.
 
They're made to work either way, as you suspected. Ease the impeller in with some vaseline or washing up liquid - I have the same engine, and that's what I do.

If it's new - all's well. But, but if the impeller is from a previous season, do check out the roots of each blade. That's where they begin to fail, with all the consequences. The end of each blade should be rounded - any wear here and it's time for a new one!

PWG
 
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Doesnt really matter.

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agree 100%

one of the advantages of having a speedseal cover is that one can open the pump and look at the impeller without worrying about gaskets every time

I took my time and inserted the impeller with the blades in one way, the other way around, half this and half that, in the end after a couple of minutes of running the engine the pump was always fully primed and all fins oriented in the same way /forums/images/graemlins/ooo.gif
 
just read your other post about the battery - at least its proven now. I didnt want to tell you that the Halfords pack wouldnt achieve anything !! /forums/images/graemlins/smile.gif

Re the lack of water, just clearing the strainer might not clear a blockage - I know this from experience of an overheating engine on the previous boat! It could be that weed and stuff has build up in the skin fitting, so even if you pulled something out of the strainer, you might still have a problem.

Trick is to open the sea cock with the filter out and cover open. You should get a gush of water, if not its blocked. Give it a good poking with something long, like a stick, which may dislodge anything on the outside and when the water then gushes in, shut the seacock quick ! Put filter back in, etc.

I would do this before testing your new impellor so that it doesnt run dry any longer than necessary.

I now check the strainer in this way on a regular basis, especially before a long period of motoring.
 
Sorted!! Thanks for all the help once again. Anticlockwise as per sailorman, (inlet to outlet the long way round), but it went in with them pointing both ways and clearly sorted itself out. Lots of hot water spewing from the exhaust, and not such a throaty noise, which is what we like to see and hear /forums/images/graemlins/smile.gif

Next ...... the leak from the deck into the aft cabin!!!

Richard
 
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Trick is to open the sea cock with the filter out and cover open. You should get a gush of water, if not its blocked.

[/ QUOTE ]

Did this and got the gush! also water poured out of the pump when I removed the cover. I think over 10 months, the impeller had sealed itself to the cover and this caused the damage.

(I think our Navtex were fitted at different times, so I dont seem to have the same kind of switching system as you have. I'll trace the power at some time and fit a switch somewhere in the line)

Thanks again

Richard
 
Easiest way I have found when fitting new impellers is to compress it with a cable tie around the middle prior to fitting. This way you can ensure all blades are bent the correct way before putting it in the pump - even though it is not that critical because they will sort themselves out when the engine is started.
A good smear of silicon grease or washing up liquid also helps alot - push the impeller in half way, cut off the cable tie and push in the rest of the way - easy peasy!!!
Also don't forget to grease the drive shaft and centre bore of the impeller to ensure it is easy to remove next time.
 
If you've got a water filter/strainer above w/l between intake & engine inlet, take the inner liner out, put a high-ish pressure hose in and reverse flush back towards the seacock - we had crud get up inside the intake last summer up the Rance, and two goes of the Port des Sablons marina water hose blew it right out.

Might work with a direct feed cooling system with no strainer by detaching the hose above the W/l?
 
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