Vibration from forward to neutral - SailNet Community
 
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post #1 of 9 Old 06-29-2008 Thread Starter
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Vibration from forward to neutral

Hey all, had a nice weekend sailing but noticed something new docking today. I went forward on slow/idle (slowest forward) and went to neutral, when we came to a stop there was a big ruckus from the engine and I thought it stalled but it didnt, the RPM came back up (wasnt looking at the tach but thats what it sounded like) and everything was ok...

anyone know what this is and is it something I should worry about ? hoping my transmission isnt causing this, it sounded more like a idle going too low...

My engine is a Yanmar 3GM30F and boat is a Beneteau, transmission is kanzai.

any tips would be appreciated !

Gaute
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post #2 of 9 Old 06-30-2008
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How's the gearbox oil lube level?
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post #3 of 9 Old 06-30-2008
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Did you wrap something on the shaft... that might cause the engine to slow and resume like that... If the rope or object wasn't too long, it would just slow the engine as it wrapped, and then it would resume power as it just spun.

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post #4 of 9 Old 06-30-2008
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I have the same engine. Low idle will do that. Minimize 1000rpm. Best to stay around 1500+ w diesels. So says jwayent@jwayent.net He's a pro.

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post #5 of 9 Old 06-30-2008 Thread Starter
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gearbox oil is fine, thogh I'm planning on replacing it soon, and I dont think somethings around the shaft. I had a look under the boat and a diver was on it just a few days ago, it was only temporary and stopped once the rpm came up... I normally go close to the continuous rating on the engine when we'r moving but when docking I go slower
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post #6 of 9 Old 06-30-2008
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gsyversen, the following link may be of use to you.

Yanmar 2GM20F
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post #7 of 9 Old 07-02-2008 Thread Starter
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interesting article, I'll post there to see how they adjusted/found how much slack there was.... thanks all !
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post #8 of 9 Old 07-02-2008
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Interesting subject

I have the Yanmar 3GM30F model also and a few weeks ago, I couldn't believe how much the thing was vibrating when idle soon after start-up. It only did this once, maybe twice, on separate occasions. Once above about 1100 RPM, the motor really smoothed out. The odd thing was, once I dropped it back into the normal idle range (700 to 800 RPM) after a few minutes, the vibration was gone. Maybe the engine was a little cold.

Since then, I don't notice it as much. I still think overall the motor vibrates more than other marine diesels, but (knock on wood), it has been very reliable for me.

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Joesaila I have the same engine. Low idle will do that. Minimize 1000rpm. Best to stay around 1500+ w diesels. So says jwayent@jwayent.net He's a pro.
I think 1000 RPM is too high for idle. I have never heard Yanmar quote that number. Most 3GM30's that I know of idle around 800 RPM.
I found this on a Yanmar reference site:

Idle Table - Yanmar Motors

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post #9 of 9 Old 07-07-2008 Thread Starter
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I'v noticed that its not so much cold engine on mine but when I quickly take it from forward to reverse, like when docking... or when just quickly putting it in neutral from forward-faster-than-slowest. this most often happen during docking and sometimes it just can't be avoided though I try my best. the link said that the throttle cable was stretched over time and it cut the idle down so much it dropped a cylinder... the symptoms sounds similar, anyone know how to adust the idle or is it just using the tach ?

Gaute
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