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Old 22-07-2013, 11:49   #1
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Yanmar 2GM: Throw it in gear and it goes. Usually.

I've dealt with this problem for years: I move the throttle control forward (it of course also engages the transmission) and the boat most often moves forward. But when it doesn't, selecting reverse and then forward usually does the trick. Sometimes it doesn't.

This can be a big deal when the wind and a break wall are situated just wrong.

I thought there might be slack in the shifter cable such that the engine was throttling up before the tranny fully engaged but this doesn't seem to be the case.

Is this a common Yanmar problem? Any diagnosis ideas out there?
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Old 22-07-2013, 12:08   #2
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That sounds more like a control lever problem rather than a yanmar problem.

What controls do you have?
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Old 22-07-2013, 12:10   #3
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Re: Yanmar 2GM: Throw it in gear and it goes. Usually.

Not a problem usually associated with Yanmars.
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Old 22-07-2013, 12:23   #4
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That sounds more like a control lever problem rather than a yanmar problem.

What controls do you have?
It's also Yanmar. My only thought is that the shift lever on the tranny is barely getting fully engaged. I should probably detach the cable, start er up, and operate the lever (on the tranny) directly, to see if it engages more often.
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Old 22-07-2013, 17:27   #5
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Re: Yanmar 2GM: Throw it in gear and it goes. Usually.

Quote:
Originally Posted by GregSteimel View Post
It's also Yanmar. My only thought is that the shift lever on the tranny is barely getting fully engaged. I should probably detach the cable, start er up, and operate the lever (on the tranny) directly, to see if it engages more often.
That control is actually just about the cheapest Teleflex control made (Yanmar rebranded). I don't doubt it's your source of grief.

Teleflex Morse - Single Lever Side Mount Sail Boat Engine Control, CH2
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Old 22-07-2013, 18:12   #6
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Re: Yanmar 2GM: Throw it in gear and it goes. Usually.

I very much dislike (hate) those single lever systems and would recommend replacing it with a 2 lever system! it will save your bow or stern and in the end it will be cheaper.
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Old 22-07-2013, 19:27   #7
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The cable would be your first bet.


We had a similar problem on a larger Yanmar. Turned out to be the forward clutch slipping. Reverse works great. We ended up having the tranny rebuilt.

We had a brief moment of excitement backing into the town dock in Camden, Me when the forward gear would not engage. Some quick line handling did the trick.

Good luck
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Old 22-07-2013, 20:07   #8
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The cable would be your first bet.

We had a similar problem on a larger Yanmar. Turned out to be the forward clutch slipping. Reverse works great. We ended up having the tranny rebuilt.

We had a brief moment of excitement backing into the town dock in Camden, Me when the forward gear would not engage. Some quick line handling did the trick.

Good luck
So you're saying that a slipping clutch could cause the transmission not to engage? Were there any other symptoms?
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Old 23-07-2013, 03:00   #9
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Re: Yanmar 2GM: Throw it in gear and it goes. Usually.

Had this problem myself some years ago. The problem was not that the clutch slipped once it was properly engaged but that the clutch would not engage at all.

I pulled the gearbox down and found that there are two thrust washers activated by bellvue springs - conical washer things, on the clutch shaft. The forward clutch thrust washer had a slight circumferential groove worn in it and I theorized that the spring and thrust washer arrangement was there in order to prevent the clutch cone from sagging and miss-aligning.

These transmissions work by having either the cone or clutch engage by traveling both axially and tangentially along the shaft - they go back and forth along a helical spline and consequently the more torque applied the tighter the cone and cup engage (This is the reason that you put the gearbox in reverse rather than forward if you want to stop the prop rotating when sailing) If one or the other of cone or cup sags on the shaft they just touch at the top and slip without fully engaging.

All I did was turn the thrust washer around so that it presented an unworn surface to the bellvue spring and I had no further problems with it. If you want new parts I would replace both thrust washers and bellvue springs however if you do this you should go through the full spacer adjustment procedure on reassembly.
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Old 23-07-2013, 07:31   #10
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Yikes. I've got a feeling you have put your figure on my problem. There's not a tighter spot to work on this boat, but I suppose I could get the tyranny out and do this.

Gotta love this forum...
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Old 02-06-2014, 16:28   #11
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Re: Yanmar 2GM: Throw it in gear and it goes. Usually.

Tranny is out, had to unbolt the rear engine mounts and lilt the engine to get at the bottom bolts, but it came out. After much research, I took it apart and replaced the clutch cone.


It appears to work, but I won't be sure until it launches. Would never have known to try this without your help. Click image for larger version

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Old 02-06-2014, 17:37   #12
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Re: Yanmar 2GM: Throw it in gear and it goes. Usually.

The slipping forward clutch is almost always due to a glaze developing on the mating surfaces. Deglazing, once you have the box disassembled, is very easy. There are quite a few threads covering this, both here and elsewhere. Do a search on deglazing Yanmar/Kanzaki transmissions and you'll learn it all.

cheers, graeme
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Old 02-06-2014, 19:34   #13
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pirate Re: Yanmar 2GM: Throw it in gear and it goes. Usually.

Subscribing ... i have same trans. Gonna get me some holy water.
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Old 02-06-2014, 20:06   #14
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Re: Yanmar 2GM: Throw it in gear and it goes. Usually.

Look here, and follow my painful process through to a happy conclusion.
If you have the box out, it's a doddle.

Not too sure about mucking around with thrust washers unless you do it properly by the book - I suspect you'll only defer the problem caused by cone glazing.

De-glazing KM2A Clutch Cones
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Old 20-08-2014, 09:56   #15
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Re: Yanmar 2GM: Throw it in gear and it goes. Usually.

Greg, Hi, this is Steve Carroll , we have two Yanmar SD50 sail drives on our St Francis Catamaran here on the Chesapeake Bay. I wondered how you resolved the clutch not engaging problem, ours just started doing this yesterday. We had the cones lapped at 750 hours a year ago....we now are at 1400 or so. I did notice that we and overfilled the transmission with Quicksilver and removed some which seems to help...any help would be appreciated

Kind Regards,

Steven & Bonnie Carroll

242 431 2222 Bahamas cell
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