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Kenomac · 05-06-2017, 10:39

How often does the water pump impeller need to be changed? I changed the impeller on our Yanmar 4JH3-HTE turbo earlier today, which was a cinch this time with the correct Yanmar extraction tool. But as you can see in the picture, it's difficult to tell the new one from the 18 month old impeller. The impeller before this one looked tattered, cracked and worn after 24 months of service.

This used one may have had 300-350 hours on it, some of them hard hours, but there it is looking like new. I saved it for an emergency replacement, but really...

How often do these things need replacement?

Another note: The cracked and worn impeller 18 months ago was doubtful if it received a lubrication when installed and we did have a minor very brief overheating (shut seacock) episode prior to replacement.

The latest two impellers were well-lubricated prior to installation.

Anders · 05-06-2017, 11:05

Mine has not been changed for at least 9 years, that's how long I owned the boat with a yanmar 3gm30. Thanks for reminding me, wrote it up on my to do list!

sailah · 05-06-2017, 13:14

I know it's overkill but I do mine every year. I remove them at haul out and place the impeller, pump cover and screws on the nav station over the winter as reminder. I save the old ones for spares. Last year I had a new impeller and when I removed in fall one of the blades was missing and I only have 6 blades.

I also lube mine every install.

Stephen Fascian · 05-06-2017, 13:29

I used to change it ever year, so about 100hrs of use, and it always looked like new, it is such a pain to change. so I started changing ever 300 hrs and it still looked good the last time I did it. I always use lots lube. This was on my Yanmar 2QM15

CarlF · 05-06-2017, 13:44

I change my Yanmar 4JH4 impeller every two years (which is typically 500 hours). They always look good. I sometimes don't lubricate them. Doesn't seem to matter. I also love the extraction tool.

My Onan genset impellers, on the other hand, lose blades after about 50 hours. At first I thought the impeller was getting dry between runs but I confirmed it is staying wet.

I wish I understood the different performance.

toddster8 · 05-06-2017, 13:46

I try to do it every year. Sometimes if I don't have any long trips planned, I might forget. In fact, I had skipped the last two years on the Oberdorfer pump because it had a non-standard screw that I couldn't get a tool on. But the old impeller looked hardly worn. (Also replaced all the cover screws with thumbscrews.)

If the old impeller still looks good, i change it anyway, but keep the old one as a "cruising spare." Unless there are already two of them in the box.

I have one Oberdorfer and one Sherwood pump. For some reason, the Sherwood seems to burn through impellers twice as fast. It would be nice to have both pumps the same, but the price of a new pump is just high enough that there's always something better to spend the money on.

Kenomac · 05-06-2017, 13:54

Anyone know how long a Yanmar water pump lasts? I'm wondering if I should carry a spare or a rebuild kit with a set of bearings. If I get a rebuild kit, then is it a DIY or do the bearings need to be pressed into place?

toddster8 · 05-06-2017, 14:23

I don't now about Yanmar, but the other makes I mentioned both seem to fail (first) by wear to the cam and to the inside of the cover plate. Such that water goes around the impeller blades instead of getting pushed out of the pump. I suppose this might be due in part to bearings getting loose. Acting on advise from another forum, I was able to revive the Sherwood pump by lapping down the cover plate on a piece of sand paper, laid flat on the bench, until all the wear grooves were taken out. We'll see how long that lasts.

I priced out a complete re-build kit and it was about half the cost of a new pump! The PO left me a complete spare pump, along with a bunch of other parts apparently scavenged off an old engine. On closer examination, they're about as worn-out or more than the ones I have in use. But especially if pressing bearings and the like are involved, refurbishing these junkyard parts, at leisure, would probably make for the easiest "on-cruise" repairs. Just swap out the whole unit. Actually executing this plan might take some effort. Darn... looks like I have to rebuild the starter on the Jeep this week. And the other car is still up on jacks, waiting for a cooling manifold.

Privleoplag · 05-06-2017, 14:32

Quote:

Originally Posted by Kenomac

Anyone know how long a Yanmar water pump lasts? I'm wondering if I should carry a spare or a rebuild kit with a set of bearings. If I get a rebuild kit, then is it a DIY or do the bearings need to be pressed into place?

I don't know how long they last but mine was leaking when I hauled the boat so I brought the pump home with me and ordered seals and bearings from the local bearing supply house. The bearings were fairly easy to remove but a bit tough to install. Used a 1/2 drive socket just under bearing size to pound the bearings in. I supposed I could have used the large vice or the shop press to press the bearings in, but whatever. It was nice to be in the shop where I had a good heavy vice to lay the pump on while I installed the bearings. I think a small vise on the boat to work on will be needed for when I overhaul the other pump. I want a small vice anyway..
One thing nice about getting the replacement parts here.. compared to oem. Saved a lot of $$$ for sure. The $32 bearing was $8 or $9, the $25 bearing was about $6, the $11 dollar seal was $4, the $4 o-ring was 35 cents. I ordered 3 sets, one for the overhaul, one for the other pump, and one set for spare.

lockie · 05-06-2017, 15:52

I have read in various sources that engine failure is one of the most frequent call-outs for towing or rescue, and that cooling failure forms a large percentage of those calls. So it seems to me that opening your CW system up annually to inspect it even if you don't replace the impellers, makes a lot of sense. If the used impeller looks good it will make a good back-up spare. The major benefit is your own increasing knowledge of and competence in repairing the system.

I had been in the habit of changing the impeller yearly and wondered if I was overdoing it. So after a 2-year hiatus, my latest service revealed a build-up of scale on the cam, that was eroding one side of the impeller lobes and would maybe have lead to bits of impeller ending up in the engine passages. So it's back to yearly to me.

If you are competent to press off and on bearings and seals (and it's not that hard - these are only littlies!) and lap any wear marks out of the shaft and cover plate with suitable grades of abrasive paper, you will be able to keep your CW pump healthy for decades with the only expenses being cheap generic bearings and seals, and OEM impellers and gaskets.

Stay cool man!

Cheers, Graeme

transmitterdan · 05-06-2017, 15:59

Quote:

Originally Posted by Kenomac

Anyone know how long a Yanmar water pump lasts? I'm wondering if I should carry a spare or a rebuild kit with a set of bearings. If I get a rebuild kit, then is it a DIY or do the bearings need to be pressed into place?

The 4jh3e pumps last for about 2K hours. Impellers last about 36 months so I replace at 24 months. YMMV because it depends a lot on the quality of water. Sandy water eats up pumps. Most strainers don't remove fine sand. If they did they would be plugged all the time. So if you are anchored a lot in shallow sandy water with wave action then the pump will ingest a lot of sand. This erodes the pump housing and abrades the impeller. Bottom line is "it depends".

savoir · 05-06-2017, 16:21

I change my Yanmar raw water impeller every two years when I also rebuild the fresh water pressure pump. It may be too short a period but that's the routine.

**a64pilot** · 05-06-2017, 16:55

Buy a new OEM spare, that way the one on your engine will last forever

bensolomon · 05-06-2017, 18:05

I have a 1990 Hunter jegend 37.5 with a Yanmar 3gmhf. I replaced the raw water pump last year because I was heading out into the Atlantic and was concerned about engine failure. I did not replace it because I thought it needed replacing. Upon removing the water pump, I had noticed that it was leaking. I presume this is the original sea water pump that came with the boat in 1990. So, in an effort to answer your question about how long they last, this particular sea water pump lasted 27 years. I have only owned this boat for the past 5 years and I presume the total hours on the engine or approximately 100 hours per year.

As for the impeller, I changed mine every year without fail. I have 5 spare impellers in my toolbox. As a side note, I put on a new mixing elbow when I put on a new sea water pump and I cleaned out the heat exchanger.

I suspect for my peace of mind, I will change the sea water pump every 5 years and then mixing elbow every 5 years for good measure and I will continue to replace the impeller on a yearly basis.

Hope that helps.

Ben