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Old 12-10-2015, 10:16 PM   #1
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Lost Impeller vanes

I changed the impellers on my motors today, Yanmar 4LHA-Stp, and one of them was pretty chewed up. It was missing big chunks of three vanes.

I know I need to get those vanes out of the system so I pulled the cover off of the end of the HE closest to the pump, just downstream of where the hose enters the HE. No vanes. I pulled the other end next...no vanes there either. Nothing in the hose between the pump outlet and the HE inlet either.

My heat exchangers have screens on them, with openings a little larger than the diameter of a pencil lead. I don't see any possible way that the broken chunks of impeller could get past them and into the tubes unless they were ground up into tiny pieces, almost a powder.

Any thoughts as to where they could be? Stuck in the pump somewhere maybe?
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Old 12-10-2015, 10:22 PM   #2
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They could be stuck right in the exit of the pump or elbow coming out of the pump if there is one.
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Old 12-11-2015, 02:41 AM   #3
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They will probably be in the hose between the pump and strainer.
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Old 12-11-2015, 02:42 AM   #4
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They have been known to hide in the supply line TO the pump, the input side, by going backwards. Suspect when the engine stops, if there is any bounce back, that may be enough.
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Old 12-11-2015, 07:04 AM   #5
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You'll find them, and don't stop looking until ALL the vanes are accounted for.
Can I ask how long the impeller was in service?
I can honestly say that in 25 plus years of boating almost all with diesels, I never lost an impeller blade. I change them before they self destruct.
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Old 12-11-2015, 07:23 AM   #6
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They say confession is good for the soul. This is what the impellers in our our two FL 135s looked like after a 900-mile trip from Florida to the Chesapeake. We monitored temperatures with an infrared thermometer every hour and the engines never came close to overheating--a testament, I suppose, to the robust cooling systems in these old engines (or maybe just dumb luck). My excuse was we were new to the boat and thought the fact that the PO had just changed them out meant they were sound. Turns out he kept used impellers and recycled them, something I'll never do again. I fished out pieces from all three heat exchangers downstream of the pump--I was amazed some of them got as far as they did. Big lesson learned.

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Old 12-11-2015, 07:44 AM   #7
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They are not in the pump, I pull the pumps when I change impellers, it's pretty much the only way to do it on my motors. I also pulled the hose elbow (it's short) from the pump to the HE as I am going to replace it. Not there either. I'll check the supply hose to the pump this morning, it is pretty long, so it is a possibility.

I've never had an impeller fail either, which is why I'm surprised. They have been in service for just short of 20 months. About 250 hours. A little longer than I usually go, but not extreme. The port side failed, the stb side is fine.

Additional clues: I'm actually sending both pumps off for a rebuild, the base plates in them are pretty worn (though the sides of the housings and the cams are fine) and they show evidence of having leaked at the weep holes in the past.

Also, at the last impeller change I installed a speed seal cover plate thinking it would make it easier to change that impeller...it didn't. But what it did do was leak like crazy on that side causing me to have to pull the pump again after about 20 hours and tighten the beejezus out of the thumb screws to get the leak to stop. When I took the speed seal off this time one of the screws sheared off in the housing, another reason to send it off for a rebuild. I'm going back to a standard cover plate. I have a speed seal free to a good home if anyone wants it.
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Old 12-11-2015, 09:30 AM   #8
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OK, I checked the entire cooling system; that is: strainer, supply hose to pump, pump, supply hose to first HE, upstream end of HE (screened), downstream end of HE (also screened), hose to transmission cooler, both side of transmission cooler (really small tubes here), hose to oil cooler, both sides of oil cooler, and upstream end of HE on top of oil cooler (not sure what that one does but it is screened as well). Next step from here is out through the exhaust. No vanes.

Maybe they migrated downstream to the strainer basket and I dumped them when I was cleaning the basket?

Where else could they be?
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Old 12-11-2015, 09:34 AM   #9
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20 months and 250 hours is nothing, the impellers should have held up better I agree.
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Old 12-11-2015, 09:35 AM   #10
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Here is the impeller.
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Old 12-11-2015, 09:57 AM   #11
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Too bad about your Speed Seal experience...mine works perfectly.
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Old 12-11-2015, 10:06 AM   #12
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Is that a Canadian Nickel in the photo!🤑
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Old 12-11-2015, 10:27 AM   #13
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Dime-Hey it's got a boat on it so it fits...
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Old 12-11-2015, 10:29 AM   #14
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Wooden, but pretty much the same worth as Cdn nickel
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Old 12-11-2015, 10:32 AM   #15
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Quote:
Originally Posted by angus99 View Post
They say confession is good for the soul.
OK I also need to confess - and my impeller is way worse than yours...

First season we owned our Mainship w/ a Yanmar 6LYA I assumed PO had not changed impeller so I ordered one from our yard - but they didn't get it in before we left on our first cruise (I was hoping it would be in at least in time to take along)

Lost cooling & hot engine alarm - shut down - towed in - and pulled the impeller to find NO vanes left intact!!
I was able to have two shipped to a local dealer and delivered to marina where we were staying.
I was obviously concerned about the amount of rubber in the system...
I carry a 1-1/2 gal wet-dry vac aboard - sucked the pump and got some pieces out of the discharge hose - next I disconnected the heat exchanger discharge at the exhaust and blew back to the pump - more pieces - repeat the above 2-3x until nothing came out - reinstalled and fine ever since.

Mechanic says they have done the same w/ water hose to back flush but I'd say either vac or water hose will work
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Old 12-11-2015, 10:46 AM   #16
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Old 12-11-2015, 01:06 PM   #17
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You guys are all wrong about the coin...I wondered if anyone would notice it. It's a Bahamian quarter.

I just don't see any way that rather large chunks of the impeller could have gotten into to the tiny openings of my HE, unless they came of in very small pieces. I didn't find any rubber at all anywhere through the entire system. Kind of a mystery.
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Old 12-11-2015, 03:07 PM   #18
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So here is tidbit of information for those in colder climates. The propylene glycol based antifreeze will harden your impellers (neoprene rubber) if you winterize the raw water system with what you run into your potable water systems. They do make nitrile rubber impellers that tolerate propylene glycol but the recommendation is to use ethylene glycol to winterize the raw water system if you have neoprene impellers. I had the impeller in my toilet harden so much from winterizing that the 12V system couldn't turn the impeller in it's housing. An impeller change immediately restored the toilet and I now use nitrile in the toilet. The engine has massive power to turn the impeller so rather than stopping the places just become brittle and break off in chunks or pieces. Good to know.
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Old 12-11-2015, 07:14 PM   #19
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One thing you can do if winterizing is remove the impeller and put it in a cup with oil. I know a few people that do it. I thought it was the cold that made them brittle but my money is on AKDougs reason.
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Old 12-11-2015, 07:44 PM   #20
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Quote:
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One thing you can do if winterizing is remove the impeller and put it in a cup with oil. I know a few people that do it. I thought it was the cold that made them brittle but my money is on AKDougs reason.
This is bad advice.

Impellers are typically made if neoprene, as the intended use of the water pump is for pumping... water. And it's cheap.

Nitrile is also fairly common material for impellers. A nitrile impeller will give less flow volume, due to its higher durometer.

Neoprene is resistant to hydrocarbon deterioration and swelling, but not immune. Soaking a neoprene impeller will make it swell.

Nitrile impellers are more compatible, but I still wouldn't soak them in oil for storage.

Comparing durometer of rubber products is only worthwhile if you are comparing the same items. Different elastomers, different brands, different initial durometer will give various feel to the flexibility of the vanes.

Some of the variation in difference of impeller life is probably attributed to variation in head pressures of different cooling systems.

Ethylene glycol is pretty benign to most elastomers, neoprene and nitrile included. Propylene glycol will deteriorate nitrile fairly quickly.
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