Yanmar impeller replacement

[DinghySailor]

Yesterday, I decided to replace the impeller on my Yanmar 3HMF to establish a maintenance baseline for my new-to-me boat. The old impeller was in good shape. I replaced it with an impeller purchased from Fisheries Supply (not a Yanmar product) that came with no seal or glycerine packet. I seated the impeller exactly as the old one, wings oriented correctly, added a new seal that I had on hand, and finished the installation. I opened the raw water seacock and I fired up the engine only to find no water coming from the exhaust hole.

Taking the pump apart again, I found one wing on the new impeller had splayed backwards (pictured). Curious. I corrected the positioning according to the original picture and confirming in the manual, reassembled, and tried again. Still, only air out the exhaust. Raw water filling strainer was confirmed. Repeating this twice more with no luck, I reinstalled the old impeller and observed normal operation.

The new and old impellers appear to be identical. The manual I’m using mentions nothing about adding lubricant. Would adding lube help the new impeller stay in position or is something else going on? Are there known issues with non OEM impellers?

 

[RitSim]

I've used dish soap as an initial and temporary lubricant for the impeller. it looks like the pump is out of the boat. I would verify that the impeller rotates when the shaft is rotated (use a pair of pliers with some rubber sheet between the shaft and the pliers so you don't create a mark that will cause a seal problem). Once you confirm the rotation, install the cover and gasket and again confirm rotation. It is possible that the new impeller is slightly thicker and is jammed when the cover is installed. Verify that the impeller core of the "new and not pumping" impeller has not separated from the rest of the impeller. I don't see a flat on the shaft. What locks the impeller to the shaft? Is there a key on the shaft?

 

[Ralph Johnstone]

There are a couple of consumables on a Yanmar that can be substituted with non Yanmar parts such as oil filters and v-belts but NEVER, NEVER, replace a Yanmar pump impeller with an off the shelf impeller. Too many stories like yours abound.

Speaking of v-belts, I would suggest that you remove any and all Yanmar v-belts and replace with top of the line v-belts which are actually much cheaper that Yanmar belts. Yanmars are top of the line engines but no logical explanation why they use junk for v-belts. Bought the boat brand new and always had belt dust until I installed Gates belts. Alignment was always perfect from day one.

Yanmar 3HMF to establish a maintenance baseline

You always want to keep an eye on the impeller but years ago I figured I better replace my impeller after 12 years of service because it was getting old. Found the "old" impeller was in perfect condition after 12 years so installed the new impeller and kept the old one as an on board spare. I now inspect the impeller every second or third year only because the gasket always needs replacement then.

I really have to wonder what the people who are replacing their impeller every year or two are doing wrong .

Use dish soap for installation as per @RitSim 's instruction. Don't use petroleum grease as it will attract and hold dirt particles to promote wear. Also, petroleum products have a habit of sometimes affecting certain rubbers. Hey, maybe that's what's screwing up all the people who replace their impeller every year .

 

[DinghySailor]

Thanks Ritsam. The pump is reinstalled and operating normally with the old impeller. The shaft is keyed. The new impeller is in new condition, not separated from core. I’ll try to get aboard again today to see if lubing the mew one is the trick.

 

[kloudie1]

Don't worry about the backwards facing impeller vane.. it will correct immediately on the first revolution.. The vane probably reversed on engine shutdown when the engine sometimes ticks backwards a few degrees just as it stops.. You can play with the pump with the cover off to prove to yourself that it is self correcting.
I have had problems on Universal Diesels with impellers that are minutely too narrow and do not seat correctly against the case and cover when installed. These will not self prime.

 

[DinghySailor]

Ralph, that’s what I suspected about the manufacturer. Thanks too for the tip on belts—I’ve noticed a lot of dust from the new belts. Now I know why

 

[DinghySailor]

Don't worry about the backwards facing impeller vane.. it will correct immediately on the first revolution.. The vane probably reversed on engine shutdown when the engine sometimes ticks backwards a few degrees just as it stops.. You can play with the pump with the cover off to prove to yourself that it is self correcting.
I have had problems on Universal Diesels with impellers that are minutely too narrow and do not seat correctly against the case and cover when installed. These will not self prime.

The problem is that it’s not doing the job, thus the post.

 

[dlochner]

Ralph, that’s what I suspected about the manufacturer. Thanks too for the tip on belts—I’ve noticed a lot of dust from the new belts. Now I know why

Too much tension or not enough tension on the belt will also belt dust.

Shameless self-promotion warning. I wrote this article on belt tensioning for Good Old Boat a few years back. A simple easy to make tool makes the job easier and faster.

Dogwatch Mail Buoy – July 2017 | Good Old Boat

goodoldboat.com

 

[kloudie1]

Agree, but the back facing impeller is not the cause.

 

[Benny17441]

Make sure the rubber assembly has not separated from the metal sleeve in the center. It will usually happen at start on when no lubricant is applied to the vanes but happens more frequent in non-oem impellers. Compare the length of the vanes and the thickness of the new impeller to old one, there is always the possibility of a wrong part for the application.

 

[Terry Cox]

NEVER, NEVER, replace a Yanmar pump impeller with an off the shelf impeller.

Agree with Ralph. Stick with a Yanmar brand impeller. Had a similar situation with our Onan Genset awhile ago. A real hair puller. They looked identical, but only the Onan brand impeller worked. You can read about my saga here to understand the importance of brand specific parts. Onan Cummins 8KW Genset Issue

 

[DougM]

Agree with Ralph. Stick with a Yanmar brand impeller. Had a similar situation with our Onan Genset awhile ago. A real hair puller. They looked identical, but only the Onan brand impeller worked. You can read about my saga here to understand the importance of brand specific parts. Onan Cummins 8KW Genset Issue

I don’t agree with that…
Yanmar uses different pumps on their engines depending on year or size. The pump on my 2GM20F was, for example, a Johnson brand. It differed from others in that it used an O ring in the cover plate instead of a gasket. Taken apart and removing the impeller for the first time, it had a Globe brand impeller. (fortunately not one of the generation that had issues with the insides detaching from the rest of the impeller). I got the new impeller at the time from a local boatyard. They matched the old impeller to the new one for dimension and attachment type and sold me an impeller in Westerbeke packaging which included extra O rings. In all the years I have been replacing impellers on that engine, I have never even seen an impeller in Yanmar packaging. Since the first replacement I have generally ordered impellers based on size and attachment from differing sources.

As for belts, its important to match both the length and the cross section dimensions. They can be any brand and purchased from a reputable auto parts store. The person at the counter has to be aware of the differences.

 

[dlochner]

Last spring I replaced the impeller on my Yanmar with a Globe impeller, no problems after 500+ hours of motoring.

One item that seem like it be replaced with a non-Yanmar is fuel line. I replaced all the fuel lines due to leaking using ¼" line. The still leaked. Bought Yanmar fuel lines and problem solved.

Yanmar fuel filters are rebranded Racors.

Gates makes a fine v-belt.

 

[mspeters]

Last spring I replaced the impeller on my Yanmar with a Globe impeller, no problems after 500+ hours of motoring.

One item that seem like it be replaced with a non-Yanmar is fuel line. I replaced all the fuel lines due to leaking using ¼" line. The still leaked. Bought Yanmar fuel lines and problem solved.

Yanmar fuel filters are rebranded Racors.

Gates makes a fine v-belt.

I have had good luck with the globe impellers (fresh water) on the miniature sized impeller on the 1GM10.
The OEM Yanmars debond from the hub in 1-2 years.

 

[jssailem]

I have no experience with the Yanmar pump...

Looking at the pump image and the fit of the impeller, it looks to me that there is minimal drag of the vanes against the pump body. That maybe the reason the water was not pumped.
I wonder if the diameter of the impeller is correct for that pump body.

I would not be concerned by the reverse vane. That happens when the vane is beyond the compression cam in the pump body. As soon as the pump starts to spin the flex in the vanes turns all the vanes in the correct direction.

I would make sure that there is water in the hose so that the pump is not running dry. If your strainer is above the level of the pump on the engine you can use it to fill the hose to the pump.

 

[Alan K]

A few years ago I began a logical process of replacing hoses on my 20+ year old 3JH3E Yanmar. I started with the raw water hoses from the strainer to the mixing elbow. While working near the raw water pump, I changed the impeller since I was crammed into the appropriate pretzel position to do the job. When all was reassembled, no water emerged from the exhaust.
After much head scratching and doing many of checks already mentioned, a friend asked if I had replaced the water hoses correctly.
As it turned out, I had reversed the hose connections so that the pump was pumping air from the exhaust out the intake.. In defense of my competentcy, the hoses fit much better the way I had installed them.

 

[Ralph Johnstone]

They can be any brand and purchased from a reputable auto parts store.

That's about as uninformed a statement as I have seen in quite some time. Do a little reading from RESPONSIBLE sources as to how belts are made and you may learn a few things.

 

[DeniseO30]

From what I have seen of Yanmar raw water pumps they are omnidirectional meaning they can pump forward or backward if the vanes dont self-correct when you start rotating the impeller by hand you could have a problem because if one is facing opposite of the other it would cause an air bubble breaking the self priming function. And yes use a Yanmar impeller and Gasket other replacements may not work cuz it could be off by a few hundredths of an inch even though they "look"okay.

 

[Terry Cox]

Agree, disagree, no matter. The off-brand impeller that was supposed to work did not. The Onan brand impeller did. Other than material color, they looked identical; even the tech that sold it to me agreed. One thing that I did notice was that when the off brand impeller was installed on the shaft it was exactly flush with the pump housing. The Onan brand impeller extended about 1/64", which is the correct amount. The gasket is about that thickness, which allows the impeller to press against the cover plate. The off-brand allowed just enough bypass to prevent the pump from priming.

As far as other parts go, belts, filters, etc., not much to comment. I use NAPA brand for fuel and oil filters and they seem to work just fine. When it comes to the more critical engine parts, brand seems to play a more important role, FWIW.

 

[DeniseO30]

Years ago I had the same problem with a "run dry" impeller, everything said it would work but it didn't, and it was not tight underneath the plate as you found out on yours, looks like you solved the problem!