Yanmar 3gm30f - heavy vibration/shaking in neutral

[jpeac2]

Hey Everyone -

otor has been running great but this morning something new developed and not sure what to make of it as I am in no way a diesel motor expert.

Motor runs with no issues in gear but in neutral it has a heavy vibration / shaking that I have not had previously.

3000 hours.

Going to hop in with goggles to take a look but thought I would see what folks here think.

Any thoughts?

 

[Don S/V ILLusion]

Motor mounts?

 

[dmax]

Could be the damper plate in the transmission, try to determine if it is coming from the bellhousing: Replacing damper plate on a Universal M25 at anchor - Cruisers & Sailing Forums

 

[Ralph Johnstone]

Going to hop in with goggles to take a look

Just make sure you're not wearing a tie.

Usually the problem works the other way around. Smooth in neutral and heebie jeebies in gear.

Other really remote maybes to check while you're down there :

- shaft coupling is tight.
- broken mount as per @Don S/V ILLusion
- place your hand on the x-mission and other parts to see if that's the source of vibration or knocking. Watch that neck tie !
- check all V belts for tension (I said this would be remote)
- check alternator, water pump for mount tightness.
- remove the main V belt and check if the crank bearing is tight.
- and that's about it, as this is so unusual.

Maybe never put the engine in neutral again ? Turn the engine OFF when you want to slow down as you come into your slip ?

 

[kloudie1]

Try engaging one decompression lever at a time.. only one then back on then the next one etc. you may have one cylinder that is not working as well as the others. Could be a too tight valve or an injector not up to snuff. If the valve clearance has not been checked, that might be a good place to start.. good luck