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Old 12-05-2011, 15:04   #1
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When Do You Change Your Impeller ?

After changing the generator impeller the other day, and removing the broken pieces from the heat exchanger, I realized I had little idea as to when to change my generator or main engine impellers.

If one doesn't put many hours on their engine I guess seasonally is OK. That's not my case however. When I do pull an impeller for inspection I replace it if it is starting the fall apart but if it looks OK I am guessing as to how much longer it will last.

So, any words of advice?

Thanks
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Old 12-05-2011, 15:28   #2
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Re: When do you change your impeller?

I change mine every season. I would guess that changing one every 500 hours would be about right. The westerbeke scheduled maintenance suggests 500 hours as a mark to check or replace. Personally, I don't believe in checking an impeller and then putting it back in because pulling it out and installing it in my opinion stresses the rubber and can lead to breakage.
http://www.westerbeke.com/aboutus/FAQ.aspx#40
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Old 12-05-2011, 16:15   #3
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Re: When do you change your impeller?

I've been averaging about 500hrs/year on my Yanmar 4JH3E for the last ten years and I've had no issues with changing my impeller one a year until recently when I found this impeller not turning because the metallic inner hub had degraded.

I'm more concerned now with the quality of the impellers that I purchase. I've had none of this type of problem with the Johnson & OMC impellers that I used before.
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Old 12-05-2011, 17:20   #4
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Re: When Do You Change Your Impeller ?

I change mine every other year.

It's a fairly easy system: on odd-numbered years I service the engine myself, but leave the impeller alone. On even-numbered years I have a mechanic service the engine, and I have him change impellers and belts.

The benefit here is that I keep in touch with my engine but that it regularly gets a professional once-over. And this way I leave the impeller for him, which saves on a lot of cursing.
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Old 12-05-2011, 17:31   #5
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Once a year. That way I remember the tricks and where it is any longer and I forget how I did it. Sadly I may need to advance the schedule not because of impellar failure but memory loss. I'm An idiot though and use expensive oil. The old impeller goes in a spares bucket.
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Old 12-05-2011, 17:36   #6
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Re: When Do You Change Your Impeller ?

Take along a spare or two for when stuff happens.
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Old 12-05-2011, 17:47   #7
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Re: When do you change your impeller?

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I found this impeller not turning because the metallic inner hub had degraded.
I'm more concerned now with the quality of the impellers that I purchase. I've had none of this type of problem with the Johnson & OMC impellers that I used before.
I think it's a fairly common failure mode. I had a Johnson impeller fail this way twice. I now replace the impeller every year, regardless of its appearance.
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Old 12-05-2011, 18:47   #8
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Re: When Do You Change Your Impeller ?

I'm with John A on this one... always keep a couple of spares in inventory for both your main and gen set. They are cheap and when they go they can severely restrict water flow in your heat exchanger or your pump itself. Like everything else they fail under the worst possible circumstances. If I saw my water temp go up even 5 degrees, i would change out the impeller at the first opportunity. Hard to see failure in the vanes many times so pull and replace with a new one every time. Capt Phil
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Old 12-05-2011, 19:13   #9
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Re: When Do You Change Your Impeller ?

Things that have occured to my impeller pump while underway:
Laid the boat over in sand/mud and damaged the impeller when it was sucked into the pump
seen a pump that had sucked a jellyfish into the impeller pump
had blades disappear
barnacles on the water intake line inside of the screen causing pump to reun dry.

I ignored the 500 hour thing and checked the condition before beginning a long passage.
One time, while underway, off the south coast of DR., I had to stop and repace the impeller blades.
I jumped on deck as I heard that dreaded DRUM. DRUM, DRUM sound.
He passed so close that my boat did a 90* turn in his prop wash, Then he got on the VHF and laughed his a** off.
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Old 12-05-2011, 19:21   #10
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Re: When Do You Change Your Impeller ?

If you change the impeller make sure you got the seal. In a pinch, chart paper will work as a seal. I always save the old impeller as a spare. It may be used but usually not failed. It's easier to change an impeller that ain't broke at the dock than one that is at sea. You get a good spare to boot.
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Old 12-05-2011, 19:37   #11
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Re: When Do You Change Your Impeller ?

I change them every year.

A sea strainer is a good investment.
Especially if you are unfortunate enough to have the Mercury Plastic sea pump.

The longer life / run dry impellers seem to not pump as much as the factory stock impellers so I avoid them.
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Old 12-05-2011, 20:42   #12
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Re: When do you change your impeller?

Quote:
Originally Posted by CaptForce View Post
I've been averaging about 500hrs/year on my Yanmar 4JH3E for the last ten years and I've had no issues with changing my impeller one a year until recently when I found this impeller not turning because the metallic inner hub had degraded.

I'm more concerned now with the quality of the impellers that I purchase. I've had none of this type of problem with the Johnson & OMC impellers that I used before.
That looks like a Globe Impeller. I have had numerous occasions to see Globe Impellers with spun hubs. I like their concept but the darn things just don't hold up as well as OEM despite likely having a purportedly better compound.

Oh and I change yearly..... To inexpensive not to...
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Old 13-05-2011, 16:15   #13
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Re: When do you change your impeller?

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I think it's a fairly common failure mode. I had a Johnson impeller fail this way twice. I now replace the impeller every year, regardless of its appearance.
Hey, Ziggy, I agree; however, the outcome in my photo was an occurance when I was in compliance with the yearly impeller replacement. They do not all seem to last a year when you run around 500 hours a year.
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Old 14-05-2011, 21:50   #14
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Re: When do you change your impeller?

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They do not all seem to last a year when you run around 500 hours a year.
Right. I typically put on less than 100 hours per year. But I do carry a bunch of spare impellers anyway.
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Old 15-05-2011, 07:52   #15
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Re: When do you change your impeller?

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Right. I typically put on less than 100 hours per year. But I do carry a bunch of spare impellers anyway.


The problem is not really replacing one if your old one wears out. The problem is the potential for engine shutdown due to overheating when the worn out impeller blows apart and fouls the water flow in the heat exchanger. Then instead of a half hour impeller change, you got a eight hour tear down of the heat exchanger and an impeller change. I think everybody should carry a spare, but have to agree that off brand impellers may not be of the same quality as the manufacturer of the engine.
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