Transmission Noise while at idle

[eapage46]

I recently purchased a 1995 Beneteau Oceanis 321. It has a Yanmar 3GM30F Engine with approx 2500 hours. I noticed that when the engine is running at idle, that there is a metallic rattling or "jingling" sound (like a small bell being bounced around) coming from the transmission, bellhousing area. This goes away when the engine is put into gear. The fluid levels are good, and there are no signs of metallic particles in the oil.
Is this a normal sound, or something I should be concerned with? I looked all over for something that may be loose and rattling.

TIA

 

[jssailem]

Welcome to the SBO Forum. TIA
Your newly purchased boat should be a lot of fun this coming season.
Boat diesel engines have what is called a "Dampening Plate". It is designed to absorb some of the torque that will rattle the gears in the transmission when the engine is running at low RPM.

If Diesel mechanics is not your first career, you might which to enlist a qualified mechanic to inspect the engine/transmission and see if they can resolve the issue

Here is some info on dampening plates.

PYI Inc. | Damper Plates

R&D Marine Damper Drive Plates are designed to prevent gearbox rattle at low engine speeds, which allows an engine to operate through its entire RPM range.

www.pyiinc.com

 

[eapage46]

Welcome to the SBO Forum. TIA
Your newly purchased boat should be a lot of fun this coming season.
Boat diesel engines have what is called a "Dampening Plate". It is designed to absorb some of the torque that will rattle the gears in the transmission when the engine is running at low RPM.

If Diesel mechanics is not your first career, you might which to enlist a qualified mechanic to inspect the engine/transmission and see if they can resolve the issue

Here is some info on dampening plates.

PYI Inc. | Damper Plates

R&D Marine Damper Drive Plates are designed to prevent gearbox rattle at low engine speeds, which allows an engine to operate through its entire RPM range.

www.pyiinc.com

Thanks John! That's very helpful. Being around automotive engines all my life, I can handle some of the basics of the diesel engine. I did notice what looked like a clutch plate in the inspection port on the bell housing. I may look into further inspection inside the bell housing.

On a side note, I'm originally from the PNW. I'm sure the sailing up in the San Juans is gorgeous.

 

[jssailem]

Yes it is wonderful. I feel blessed to be able to sail and enjoy the waters of the Salish Sea.

 

[Benny17441]

Play a little with the transmission lever and see if the shifting cable needs adjustment.

 

[kloudie1]

If you have to replace the damper, you'll have to pull the back cover off the bell housing and remove the gearbox in one piece. The box and cover weigh only 40 pounds or so but you need 4-5 inches to move the box aft to clear the shaft spline from the damper. If the prop shaft can't move that far aft, you may have to release the aft engine mounts and tip the engine up enough to get the box to move aft over the shaft.. and if ya don't have room to do that, the whole engine can usually be moved forward just enough (after releasing it from the mounts) without having to move wires and or hoses.. Good Luck with it.