Impeller replacement

Maine Sail · Jul 6, 2009

You may need..

Roy10289 said:
I removed the cover plate from the impeller on my Yanmar 3JH2E diesel this week. Wanting to replace the impeller as a preventive measure I tried to remove it but found no clearance from thr starter motor to do so. Before I pull components off,I would like advice from someone who has done this on the Yanmar engine. I have read the very heapful post from Main Sail about changing impellers, however ,on my engine there is no room to pull the old impeller out. Please advise....

You may need to pull the pump. On many of the older Yanmar's you need to remove the pump from the engine to get enough clearance to work on it because Yanmar installed it backwards. If I remember correctly there are only two bolts to remove to get the pump off. While not particularly difficult it is an extra step. On the newer models they finally changed this.

Ron McCoy · Jul 6, 2009

I also have the 3JH3E Yanmar on my Hunter 386. Changing the impeller is a test of dexterity and gymnastics. Remove the engine cover completely so you can access most of the engine. Put your whole body over the engine and gingerly remove the 4 screws from the impeller plate. The next part is a little difficult. Take needle nose pliers and pull the impeller off the spindle. This will most likely destroy the impeller, but it's the only way short of a small impeller puller to get it off. Next time you put in a new impeller, liberally coat the shaft and impeller with waterproof teflon grease. The impeller will come out much easier next time. Using a little body english, some cussing and a cut finger or two you'll get the impeller off and a new one installed. Note the proper direction of the impeller and replace the plate. Replace the plate with a "Speed Seal" will make the installation a little easier, but Hunter didn't design the yanmar for "easy maintenance". A port access along the bullkhead adjacent to the head would have made this task a 30 minute job versus an all day frustration. Best of luck regardless.

DougM · Jul 6, 2009

I replaced my water pump impeller on a Yanmar 2gm20f and found it easiest to just take the entire pump off and replace the impeller at the workbench.

My engine is the YEU variant and had a Johnson water pump. Because that pump has a plate with an "O" ring groove in it, I didn't feel the need to purchase a Speedseal kit. That kit is really a nice addition if you happen to have a pump that originally had gaskets.

tsmwebb · Jul 6, 2009

Ron McCoy said:
... liberally coat the shaft and impeller with waterproof teflon grease. ...

For a while now I've been using Johnson Pump "MC97 longer life" impellers and they come with a bit of glycerine for lubing and recommend against using grease... Worth reading the instructions first anyway. I take the pumps off to change the impellers, too.

--Tom.

Allan Frey · Jul 6, 2009

I have the 3jh2e in a H376 and have replaced the impeller a number of times.

First, I cut a hole in the head wall and installed a 20 inch plastic hatch which is easy. This gave me full and easy access to the impeller, starter, alternator, wiring etc.

Then it is simple to remove the impeller plate screws. Then use a 90 degree (important) needle nose pliers which you can get from an auto store, it is about 8 inches long. You can then wriggle off or also use a screw driver with the pliers to lever out the impeller. Then use a plastic tie to compress the vanes of the new impeller. You can lube the inside of the housing, shaft and the new impeller with ky jelly or superlub. It will then slip in and the tie will slip off as it goes in. Reinstall the cover plate.

Allan

Allan

Cpt. Jon · Jul 7, 2009

I replaced my raw water side impeller on my 2QM15 while the pump was installed and I still don't know how I finished, it was nearly impossible to do with the pump installed. When I went to do the fresh water side I removed the pump and it was sooooo much easier, I will always remove the pump from now on.

BobM · Jul 7, 2009

Removal of an aft facing pump may be required. If you are concerned about changing it out on the fly in a hurry, the best option is to keep a spare pump on hand ready to install. Not a CHEAP option though...

Don12364 · Jul 7, 2009

My 3JH2E Impeller Experience

On my H376 I only needed to undo the 2 alternator bolts and move it forward without undoing the wire connections.
Then I removed the 4 off M6 screws from the pump cover and prized out the impeller using 2 small screwdrivers.
I then modified the pump plate with a file as per the diagram below so the 2 lower bolts remain in place and guide the plate back in to place (All before the days of "SpeedSeal"). I should have replaced the screws with allen heads but didn't bother.
All this to make life easier for next time.
I felt the Yanmar designer must have understood the impeller, as mounted, was going to be difficult to change and because it looked to be much less stressed than ones on their smaller engines, I wrote to Yanmar to ask for the design life of the impeller. They ignored my request so I decided to run the impeller until it failed. Stupid I know but I do carry a spare as well as the original which I changed as part of the service schedule.
All this was in AUGUST 1999 and well over 1000 engine hours ago and it is still going strong - but I still worry, and when my nerve fails I will take it out to see its condition.

Likewise I have had the exhaust injection bend out 3 times with nothing wrong so I am waiting till I get trouble. At least this should be a progressive loss of power.

IMHO these Yanmar engines are far more reliable than we give them credit for.

Impeller replacement

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