Transmission Issue strange noise.

[Clydo]

While running engine at the dock 2500 rpm in gear (ok at my marina) after
warm up and about five minutes later went below to check stuffing box
drip status. All good and started up steps when heard loud "thunk thunk and
thunk in eng/tranny compt. Up quick like a bunny to shut down engine. Noise like someone
hitting hull bottom or wood siding with 4 x 4 not a metallic clang. Checked eng and tranny
and all external looked ok. Have had problem with gear shift sticking fwd
and reverse but feel that a cable problem. Started eng up and ran in same
conditions fwd and reverse and could not repeat noise. No obvious wood or debris in slip or astern. No excess eng vibration before or after. Was this
"damper" problem whatever a damper is? 2003 year boat with 325 eng hours. All wild eyed guesses appreciated.

Clyde Thorington
C310 # 245
ILEAN TOO
San Jose, CA

 

[Long Story]

Odd question - why were you running the engine at 2500 RPM at dock in gear? I don't power at hull speed near those RPM's in open water?

 

[Long Story]

From the manual

 

[dparilla]

Having just had the same noise...did it sound like a fishing weight banging on the hull? If you weren't chopping a piece of wood with the prop... I would bet on the drive train. We ended up losing our damper plate that connects the fly wheel to transmission about an hour after we first heard the noise. The noise stopped and everything seemed fine, but when it happened again, the prop stopped turning. If you search my post "stupid transmission" you will see the end result. I am waiting on the new plate to arrive and will install it as soon as I can.

Even if the problem ends up being in the transmission (which I doubt only because they are so small that there is not a lot of room to generate the hollow thud that a damper plate letting go can), you will still have to replace the damper plate or most manufacturers/service shops will not provide a warranty coverage on the transmission work. Also, When ours went it essentially detonated, throwing fragments all around the bell housing; there was almost nothing that resembled a spring other than a few curly q pieces of metal. I ended up removing the damper plate, and the flywheel adapter plate since some of the shards of metal ended up all over the place.

 

[Clydo]

Odd question - why were you running the engine at 2500 RPM at dock in gear? I don't power at hull speed near those RPM's in open water?

Good question. Had large raft of water hyacinth heading my to block slip so used
prop wash to push it away another direction.

Clyde Thorington
C310 # 245
ILEAN TOO
San Jose, CA

 

[Clydo]

Having just had the same noise...did it sound like a fishing weight banging on the hull? If you weren't chopping a piece of wood with the prop... I would bet on the drive train. We ended up losing our damper plate that connects the fly wheel to transmission about an hour after we first heard the noise. The noise stopped and everything seemed fine, but when it happened again, the prop stopped turning. If you search my post "stupid transmission" you will see the end result. I am waiting on the new plate to arrive and will install it as soon as I can.

Even if the problem ends up being in the transmission (which I doubt only because they are so small that there is not a lot of room to generate the hollow thud that a damper plate letting go can), you will still have to replace the damper plate or most manufacturers/service shops will not provide a warranty coverage on the transmission work. Also, When ours went it essentially detonated, throwing fragments all around the bell housing; there was almost nothing that resembled a spring other than a few curly q pieces of metal. I ended up removing the damper plate, and the flywheel adapter plate since some of the shards of metal ended up all over the place.

Think probably heavier then fishing weight. More like really heavy piece of wood
" 4 x 4 " banging around in eng compartment. Not metallic.

Sounds like we may have same problem.

Clyde Thorington
C310 #245
ILEAN TOO
San Jose, CA

 

[dparilla]

Not a particularly difficult fix, but time consuming, and will require an prop shaft to engine alignment. Go slowly and methodically.

 

[RIVERCRUISER]

Must the boat be hauled and this repair completed on the hard, or can it done afloat?

I think I had this same noise running the engine (2GM20F) in gear at dock to check stuffing box drip rate. Intermittent Thumping noise and vibration.

I did not investigate any farther since it was my last little job to do before leaving for home and had no time remaining.

Have not run the engine since...

 

[rpwillia]

You can do it all at the dock

Must the boat be hauled and this repair completed on the hard, or can it done afloat?

No need to pull the boat unless you are concerned about the Cutless bearing or the prop. Everything from the coupler forward can be done on the water.

 

[RIVERCRUISER]

No need to pull the boat unless you are concerned about the Cutless bearing or the prop. Everything from the coupler forward can be done on the water.

Thanks.

 

[dparilla]

Here is the other damper plate link I posted, complete with my step by step guide.
http://forums.oday.sailboatowners.com/showthread.php?t=163160

 

[RIVERCRUISER]

Thanks, I did read that thread.

 

[dparilla]

Good Luck to you. It was nowhere near as bad a job as I had expected, but I will say that having a good cordless impact driver was absolutely essential to the repair.