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Old 05-12-2020, 07:22   #1
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Yanmar 2gm20 disassemble problem

OK, so I broke off a water pump mounting bolt so need to remove the timing gear housing. The manual says " remove the cap at the timing gear case end and remove the fuel injection pump by moving the governor second lever while observing thru the hole" Before I create a problem, what else do I need to know? The cover is the raised dome in the attached pic?

Second, it says "Loosen the hexagon bolt with the hole and remove the straight pin from the manual starting handle" What bolt are they talking about and "the manual starting handle"????
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Old 05-12-2020, 16:21   #2
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Re: Yanmar 2gm20 disassemble problem

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Originally Posted by Sailorman Ed View Post
OK, so I broke off a water pump mounting bolt so need to remove the timing gear housing. The manual says " remove the cap at the timing gear case end and remove the fuel injection pump by moving the governor second lever while observing thru the hole" Before I create a problem, what else do I need to know? The cover is the raised dome in the attached pic?

Second, it says "Loosen the hexagon bolt with the hole and remove the straight pin from the manual starting handle" What bolt are they talking about and "the manual starting handle"????
No, the cap is not the raised dome in your pic.

I have modified your pic by adding a red arrow. The red arrow points to the cap in question.

The raised dome covers the manual starting apparatus (if fitted). The yellow arrow in my attached pic shows what it looks like when the engine is supplied with a manual starting handle (ie no raised dome). Note, the water pump has been removed in my pic.
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Old 20-05-2021, 12:10   #3
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Re: Yanmar 2gm20 timing cover disassemble problem

Wotname - thanks, I am finally back onto this project. Your red arrow seems to point to the levers on the side, did you mean the large one with the wire on it? And does the fuel injection pump just lift out or is there something I need to be careful about? I see it says remove "the fixing nut of the fuel injection pump" what is a fixing nut? Then it says to "open the oil supply hole" - what is that? Next, "move the governor lever 2" Do they mean the throttle arm? Is there a governor lever 1?
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Old 20-05-2021, 16:52   #4
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Re: Yanmar 2gm20 timing cover disassemble problem

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Wotname - thanks, I am finally back onto this project. Your red arrow seems to point to the levers on the side, did you mean the large one with the wire on it? .......
I found a better picture of the 'cap' or cover. See the green boxes and arrow on the attachments.

More on the gov levers later.
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Old 20-05-2021, 17:01   #5
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Re: Yanmar 2gm20 timing cover disassemble problem

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........ Next, "move the governor lever 2" Do they mean the throttle arm? Is there a governor lever 1?
This diagram details both gov levers (red circles). The throttle arm is called the 'speed control' in this diagram.

While the picture shows a 3GM30 injector pump, the 2GM20 arrangement is the same.
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Old 20-05-2021, 17:08   #6
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Re: Yanmar 2gm20 timing cover disassemble problem

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...... Then it says to "open the oil supply hole" - what is that? ............
This applies only to the 1GM10.

The 1GM10 oil filler hole/cap is on the front timing cover and allows access to some of the governor bits and bobs.

The 2GM20 oil filler hole/cap is on the rocker cover (as you know ).

EDIT: For clarification, I found a picture of the 1GM10 timing cover showing the said 'oil supply hole' (red circle).
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Old 20-05-2021, 17:25   #7
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Re: Yanmar 2gm20 timing cover disassemble problem

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....... And does the fuel injection pump just lift out or is there something I need to be careful about? I see it says remove "the fixing nut of the fuel injection pump" what is a fixing nut? ..........
Fixing nut - Japanese speak for the four nuts that hold the injection pump in place.

As for precautions - I am going on memory now and that can't always be relied on. IIRC, the injection pump just lifts up. The only connection between the injection pump and the governor assembly is between the fuel control rack and the governor lever #2. But please, do look carefully first and confirm!
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Old 20-05-2021, 19:23   #8
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Re: Yanmar 2gm20 disassemble problem

thank you very much!!! Installing the saildrives this weekend, timing cover comes off Monday. I really appreciate your help.
Ed
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Old 22-05-2021, 22:34   #9
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Re: Yanmar 2gm20 disassemble problem

Hi Ed
The pump just lifts out but will try to get out by itself due to the pump cam follower springs, at least one will be loaded.
The rack pin and governor link needs to to line up with a special cutout on the engine housing and you move the rack by operating the stop control lever.... not a large movement though.
There is a warning regarding re assembly. If the rack pin misses sitting into the yoke on the governor link you will have either an uncontrolled overspeed ..... or a no start depending on which side of the yoke the rack pin chooses. It is possible to see the pin and yoke alignment but be aware of the possibilities.
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Old 24-05-2021, 10:44   #10
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Re: Yanmar 2gm20 disassemble problem

SkipperPete - thanks for the warning and explanation. Starting this today.
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Old 25-05-2021, 14:34   #11
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Re: Yanmar 2gm20 disassemble problem

OK, was a struggle to get everything undone (rust) but I got the 4 fuel pump studs out but no movement on the pump. I tapped slightly with a small chisel and hammer at the 3 corners hitting the gasket which I realized later were the shims. I got it up about 1/8", then used some screwdrivers to pry it up, got one side up about 1/4" and it rocks back and forth like something is holding it. Looking in the side cover ( thanks to Wotname) and I see the arm and what I believe is the rack. I tried moving both the throttle lever and the stop lever, neither seemed to have any effect. I have learned never to force something because that usually breaks something expensive.



Am I missing something?
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Old 13-06-2021, 11:50   #12
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Re: Yanmar 2gm20 disassemble problem

Any luck with getting the pump out Ed? I am dealing with the exact same problem.


Will McVay
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Old 13-06-2021, 12:59   #13
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Re: Yanmar 2gm20 disassemble problem

The manual start shaft is under the domed cap in your original pic. You’ll still need to remove the split pin in that. You probably could carefully drill out the broken water pump bolt and put a helicoil in the hole with some RTV silicone and avoid all this......
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Old 13-06-2021, 17:28   #14
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Re: Yanmar 2gm20 disassemble problem

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Any luck with getting the pump out Ed? I am dealing with the exact same problem.


Will McVay


Hi Will
You will need to get the rack control pin into the extraction “window” then it should lift out with a bit of a wiggle. Sometimes the shim pack interferes with the process but they usually remain in place. If the injector pump has a stuck plunger you won’t be able to move the rack and may need to remove the delivery valve holder assemblies and try to free up the offending plunger..... very carefully.
Pete.
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Old 15-06-2021, 13:01   #15
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Re: Yanmar 2gm20 disassemble problem

Willie, once you are released from the shims, you need to get the fuel control rack( circled in blue below) centered under the pump. Remove the side access cover and crane your head to look inside. Follow Skipperpete's comments and it comes right out. Same for putting it back together.


Boatguy, turns out the bolt snapped off inside the aluminum housing, the threaded section was clear of the cast iron case. Once I had it up on the milling machine, was easy to drill out. I probably could have drilled it out from the outside but I was sure the problem was in the main case.
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