Yanmar 4JH Engine Owners: READ THIS !

[Daedalusk]

Recently I started a thread about raw-water pumps on the Yanmar 4JH engine. Some of my contributions to that thread were based on false information given me by a pump supplier. Here is the result of further investigation.

I have been quoted prices for a Yanmar 4JH raw-water pump ranging from $723 to $803. I have the one I removed from my engine.
I have also been quoted prices for a Yanmar 3JH raw-water pump ranging from $195 to $268. I bought one for $195.

Each of these pumps is on my bench right now. Despite what I was told by a dealer, these pumps are identical in the housing and in all internal parts. On the manufacturer's parts list, the numbers are identical without any reference to the engine. This is confirmed by my own observation and measurements of the pump components.

Every part is interchangeable between these two pumps except two: the discharge port hose coupling (straight vs 90 degree) and the external drive gear.

These two parts can easily be moved from one pump to the other. If you do this you can reduce the cost of replacing the 4JH pump from more than $700 to less than $300.

If you want an engine ready spare pump, you can purchase a 3JH pump for about $250, a straight hose coupling for about $17, and a 4JH pump gear for about $132. Install these two parts on the 3JH pump, and you have a 4JH pump for approximately half the cost of a 4JH pump from a dealer.

The dealers tell me this price disparity is dictated by Yanmar as each of the pumps is a proprietary version of a Johnson Pump. I have no information on that, but the fact that a Johnson pump dealer falsely told me there were internal differences in the two pumps gives cause for doubt.

[iluvteak]

Nice to hear. I wonder if there is a similar swap for the exhaust manifold/heat exchanger? Mine just corroded out near the exhaust elbow connection on a 4jh2e....ugh

[rebel heart]

Hey that's awesome man. I've got a 4JH2E myself; thanks for the heads up.

[Daedalusk]

If any of you guys/gals want more information about this pump reconfiguration, call (850) 785-5002 and ask for Jimmy Buss. He is my parts man who figured all this out.

[delmarrey]

So which part # did he sell you at $195? The 129271-42501 or the 129670-42512

[bstreep]

Oooh. THANKS for the info - I may just have to buy a spare.

[Daedalusk]

Here are the part numbers for the two pumps:
Yanmar 3JH Pump Assy: 129670-42512 (Costs about $260)
Yanmar 4JH Pump Assy: 129271-42500 (Costs about $750)

You can turn the 3JH pump into a 4JH pump by either moving the drive gear and outlet connection from your old 4JH pump to the 3JH pump, or by purchasing a new gear (Part #129271-42700 for $132) and a straight discharge connection (Part #X01357681 for $22), and putting those on the 3JH pump.

Either way you have a seawater pump for the 4JH engine at half or less of the cost. Hope this will help some of your guys/gals.

[Loquat]

I have a 4j also. This is why I come to this website. Thanks.

[delmarrey]

If one looks at the parts list for the 3JH-4JH it shows both pumps.


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[bertho]

guys,
I have a 4JHDTE
just be careful with one detail, the drive gear is very difficult to change without access to proper workshop, the gear is probably fit hot ( but not to much) on frozen shaft I presume, is no key and you need to remove this gear to change the main bearing, It's almost impossible to change by yourself.. I have two shaft/gear destroy in the philippines by local mechanic.!!
Yanmar sell the shaft+gear+main bearing already together..
also the impeller don't have the same number of blade, 9 on the original yanmar(the expensive one), jonhson impeller have more blade 11, you will get different volume/pressure with non original impeller , don't know if really a problem?
FYI
best rgds
bertho
Nigel Irens 50' schooner

[50gulfstar]

Hi Group
Its my understanding,most JH series parts are interchangable.
Richard
Irwin43
Crisfield,Md.

[Daedalusk]

To Bertro - the gear drive on the Yanmar 4JH raw water pump is not "hot" fit or "frozen" fit on the shaft. The gear and shaft have a taper on their mating surfaces, and there is a key. The gear is easily removed with a small gear puller, or even by surporting the gear with your hand and tapping the shaft with a brass hammer. I have done it.

[speedoo]

Originally Posted by Daedalusk

If any of you guys/gals want more information about this pump reconfiguration, call (850) 785-5002 and ask for Jimmy Buss. He is my parts man who figured all this out.

Thank you so much. I've just bought a used 4jh2 turbo. You've made my day!

[bertho]

dear 4JH lover..
perhaps yanmar improve the shaft gear system, but the one I have (4JHDTE ) don't have any taper or key, will be too easy !! I manage to run temporary ( 1500nm) with drilling gear/shaft to insert a screw as key, but I can tell you the one I have was dam frozzen on the shaft .
I purchase now the original new shaft/gear and hope to keep this one until the end !
rgds
Bertho

[delmarrey]

The parts list does show a tapered end shaft with a woodruff key. So a small gear puller, or supporting the gear and rapping the shaft with a brass or lead hammer should suffice. If corroded then a pre-soaking in diesel fuel or Kroil should help.



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