Yanmar 1GM10 gearbox/clutch problem

J

jrussill

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Hi all,

We have a problem with our gearbox/clutch on our 1GM10. When setting off, usually from cold, there's very little drive getting to the prop either in forward or astern. After a few minutes there's (sometimes) a clunk and she's up to full power. Having read some posts of similar problems, I'm going to check and change the gearbox oil. Other than this, does anyone else have any solutions from similar experience? I can imagine it probably is something to do with the clutch, but are these cone clutches actually in the oil?

Thanks as always for any advice.
Jon
 
Certainly changing the gearbox oil is worth a shot, as is checking the adjustment of the operating arm at the gearbox end and trying to manually engage and disengage it to see if it is dropping into immediate correct engagement only once underway or when the oil is warm.

Richard
 
jrussill said:
Hi all,

We have a problem with our gearbox/clutch on our 1GM10. When setting off, usually from cold, there's very little drive getting to the prop either in forward or astern. After a few minutes there's (sometimes) a clunk and she's up to full power. Having read some posts of similar problems, I'm going to check and change the gearbox oil. Other than this, does anyone else have any solutions from similar experience? I can imagine it probably is something to do with the clutch, but are these cone clutches actually in the oil?

Thanks as always for any advice.
Jon
Click to expand...

Not sure why you ask but the cone clutches just dip into the oil.

As Richard says well worth looking at the operation and and adjustment of the shifter mechanism.

There are two different versions of the gear box fitted to the 1GM10, depending on age . The shifter mechanisms are rather different.

All described in detail in the Service manual at https://www.manualslib.com/manual/791391/Yanmar-1gm10.html
 
Had a similar problem on my 3GM30. It would clunk into gear.
Eventually found the revs needed to be 900 rpm at idle to allow for smooth gear engagment.
Thanks Mac
 
Last edited:
RichardS said:
I can understand why worn splines would "clunk" but I'm not sure how they could "clunk" and engage after a few minutes. :confused:

Richard
Click to expand...

The wear on the splines effectively prevents the clutch from fully engaging in the first instance, but you will find it will ride over the wear point at some period, the "clunk" is the sudden take up of the drive.
 
third engines said:
The wear on the splines effectively prevents the clutch from fully engaging in the first instance, but you will find it will ride over the wear point at some period, the "clunk" is the sudden take up of the drive.
Click to expand...

Curing it then would require a new output shaft? Maybe also a new clutch cone ? And forward and reverse gears too if the clutch faces themselves are badly worn?

I wonder if de-glazing the clutch mating surfaces would be sufficient to overcome the problem ???
 
VicS said:
Curing it then would require a new output shaft? Maybe also a new clutch cone ? And forward and reverse gears too if the clutch faces themselves are badly worn?

I wonder if de-glazing the clutch mating surfaces would be sufficient to overcome the problem ???
Click to expand...

The cone clutch models do not seem to be a problem as the splines are helical cut. The older boxes had a multiplate (a la motorbike clutch) which caused the probs.
 
third engines said:
The cone clutch models do not seem to be a problem as the splines are helical cut. The older boxes had a multiplate (a la motorbike clutch) which caused the probs.
Click to expand...

But the question is about a gearbox , with cone clutches, attached to a Yanmar 1GM10. Presumably a KM2P or KM2C
Not therefore related to wear of the splines

If it was mine I would be looking at adjustment or wear of the shifter mechanism, including operation of the remote control.
 
VicS said:
But the question is about a gearbox , with cone clutches, attached to a Yanmar 1GM10. Presumably a KM2P or KM2C
Not therefore related to wear of the splines

If it was mine I would be looking at adjustment or wear of the shifter mechanism, including operation of the remote control.
Click to expand...

But does o/p know for certain that the gbox is a cone clutch model?
 
Contest1 said:
Had a similar problem on my 3GM30. It would clunk into gear.
Eventually found the revs needed to be 900 rpm at idle to allow for smooth gear engagment.
Thanks Mac
Click to expand...

Hi Mac, I'm still working on this gearbox problem.
If the problem's to do with the revs, I'm interested to know whether it's caused by them being too low or two high. When you say that the revs needed to be 900 rpm at idle, did you have to adjust up or down to achieve this? I've found that mine is idling at 1050 rpm so will try to get it down to 850-900 rpm and see if that helps.
Cheers, Jon
 
I managed to smash up the transom of a wooden Eventide as I came out of a berth, confidently putting my 1GM10 into fwd to correct my stern way, to correct my stern way, TO CORRECT MY STERN WAY ---- CRASH .

Nearly did it again in more familiar surroundings, of course my close quarter boat handling skills had gone to pot.

No, explained my engineer, who quickly removed a shim, and lo , my boat handling skills recovered.

Don't go asking me about what shim, others here will know, or at least the right one will. !
 
I had a similar problem with the gearbox on my 1GM10. It would sometimes not engage from cold but also often seem to slip out of gear quietly. For no apparent reason it would then re-engage with a clunk.

I took the gear box off and sent it to French Marine in Brightlingsea. They said the symptons were classic indications of clutch cone slippage. They lapped the cone back into the gears and I’ve had no problems since
 
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