Tranny decoupled while under way!

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L Baker

Twist and shout

We went sailing yesterday, and I went down and watched the shaft while motoring at 3000rpm. The engine seems pretty stable, but there is about a .25" vibration at the packing gland along the shaft (i.e. the shaft and the gland around it are vibrating about .25"). Also, while we were idling, I watched the engine and, while I have been told that "two cylinder diesels just do that," it seems to jiggle around a lot at about 800rpm. The engine mounts all seem in good shape (about 2 years old, only 80h on the engine) and the mount bolts seem secure. Thus I can only conclude that, if the engine is vibrating excessively at idle, in neutral, it must be due to some internal issue. But, to my immature eye, everything seems to be working: both cylinders firing, etc. I have no sense of relativity. Should I see *any* vibration while under way at 3000rpm? Conversely, while idling at 800rpm, how much vibration *should* I expect? I haven't aligned the shaft yet, but I did tighten down the packing gland. It now drips at a reasonable rate while under way. Best regards, Larry
 
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Steve Dion

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Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
Now that you have all of this FREE advice.....

Larry: Now that you have all of this free advice, I would suggest that you find a YANMAR mechanic (not a diesel maniac) to check things out. He could analyze what you are seeing to tell you if things are correct or not. This is probably going to cost you 2 hrs of labor ($150 est). When he leaves you will have a good idea of what is up. He can also train you on how to service the engine (oil change and filters). These engines do wiggle a little at idle. They do have a vibration around 1200-1400rpms. You are going to get some movement in the shaft area between the motor mounts and the vibration. These engines are also NOT cheap. You have a big investment here and spending $150 to find out if you have a problem or not, can and should be looked at as insurance. Good Luck!
 
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Ray Bowles

Soap stone jig. Larry you can also take a

piece of soap stone in a holder and advance it up to the shaft, while turning, in very small increments and if your shaft is bent it will mark one side of the shaft and not the other. The same can be done with a dial indicater if you have access to one. This is a fairly good down and dirty test while in the boat. Just be damn careful not to get tangled up in the moving machinery as it could ruin an otherwise good life. Ray sv Speedy
 
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