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Old 30-05-2011, 01:42   #1
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Warning - Check Your Impeller

I usually change my impeller every year, despite Yanmars recommendation that 2 years is OK.
It always looks fine and easy to think its a waste of time, but I have seen a few engines damaged and its no fun trying to find bits of impeller downstream.
Today after 14 months and 150 hours this one was close to loosing a vane.

It was a Johnson impeller, previously I have used a Jabasco or Yanmar one.
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Old 30-05-2011, 02:09   #2
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Re: Warning check your impeller

If you do change your raw water impeller and find that one or more of the little "vanes" have broken off - you need to find them!
- - Starting with the piping leaving the water pump">raw water pump, take each piece apart if there are any sharp bends in the pipes and check for vanes lodged in the corners of the bends. Then open up the end of the heat exchanger and remove all the vanes that have made their way there until you have accounted for all the missing vanes.
- - Failure to do this will normally result in a "hot" running engine due to reduced raw water flow through the heat exchanger and subsequently through the exhaust raw water injector. That can lead to overheating in the rubber exhaust hose and failure of the hose.
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Old 30-05-2011, 04:13   #3
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Re: Warning - Check Your Impeller

Yea, I use to own a Niagara 31 and the first time I had to change the impeller I found missing vanes. The engine had begun to run hot so we started to look for what we excepted was a vane or two downstream. Found about a DOZEN in the heat exchanger! Obviously the impeller had been changed a few times by the POs but nobody had bothered to look for the vanes. It a wonder any water at all was getting through.
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Old 30-05-2011, 05:01   #4
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Re: Warning - Check Your Impeller

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Originally Posted by noelex 77 View Post
It was a Johnson impeller, previously I have used a Jabasco or Yanmar one.
While Yanmar certainly markets an impeller with their name on it, they do not manufacture impellers. The impellers that come from Yanmar are supplied to them by the pump manufacturers, which on Yanmar engines are almost exclusively Jabsco or Johnson.
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Old 30-05-2011, 07:27   #5
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Re: Warning - Check Your Impeller

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Originally Posted by doug86 View Post
While Yanmar certainly markets an impeller with their name on it, they do not manufacture impellers. The impellers that come from Yanmar are supplied to them by the pump manufacturers, which on Yanmar engines are almost exclusively Jabsco or Johnson.
As you say the Yanmar impellors are rebadged although there do seem to be some poor copies as well.
The genuine Yanmar one also comes with a neat central thread which allows a simple bolt to work as an impellor puller. They usually come out easily without this, but if the impellor needed changing in a hurry it would help.
No one here sells the genuine ones, which probably means they are much more expensive. I stick to the respected names like Johnson or Jabasco, but after the latest impellor I think i will stay with Jabasco although its only 1 sample which probably doesn’t mean much.
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Old 30-05-2011, 07:59   #6
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Re: Warning - Check Your Impeller

Good advice! Amazing how the engine can be gushing out water even with a damaged impeller:
THE BIANKA LOG BLOG: Lessons learned: The raw water impeller.

But, it could be just one or two vane failures away from a real problem at a really bad time.
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Old 30-05-2011, 08:15   #7
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Re: Warning - Check Your Impeller

another issue with impeller pumps are the lip seals on the inside of the pump housing,which will leak copious amounts of water once the spring corrodes.

a neat little trick to get you to port if you dont have a spare is to clean out the corroded spring debris and find a nice snug fitting o ring,push this down the shaft and over the "lips",hey presto! no leak!

i find this will extend the life of a lip seal,so even when fitting a new seal i remove the spring and replace with an o ring,making the whole seal corrosion free......
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Old 30-05-2011, 12:40   #8
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Re: Warning - Check Your Impeller

Do any of you skippers use a "post-pump, pre-block" filter basket? I've found bits of plastic, bits of seaweed and biological elements that fall under "other" in there, even though I have a functional strainer on the hull.

Like this (1/2" model...it's an Atomic 4):



No impeller chunks as of yet.

Please note this is different from a raw water strainer of the Perko/Groco kind as it's not meant to keep debris out of the impeller (although it does!), but to keep the impeller out of the block. Like the Perko glass and bronze jobs, it goes just above the the waterline, with pump pressure providing the flow.
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