“Clacking” noise on SP 135

Does it ever fail that when you’re getting ready for a trip things start to break? Hopefully, this isn’t one of those times. There’s a “clacking” noise coming from the rear of our starboard Lehman. It’s not as loud as a knocking rod bearing, but seems a bit louder than “normal” valve noise.

It seems to come from the extreme rear of the engine—by the flywheel (if there is one). I did just change the oil and it only took about 12 quarts to reach the high level on the dipstick (vs the 14.5 quarts American Diesel recommends). So maybe it’s low? When I shutdown and restarted, it seemed to be noticeably quieter. The port engine has no similar noise.



Any thoughts?

How many hours on the damper plate? Those have a definite lifespan, are between the engine and transmission and can make quite a racket if one or more springs are broken. On the plus side they're pretty straightforward to change and not too expnsive.

Ken

Beat me to it.

kchace said:

How many hours on the damper plate? Those have a definite lifespan, are between the engine and transmission and can make quite a racket if one or more springs are broken. On the plus side they're pretty straightforward to change and not too expnsive.

Ken

Click to expand...

Each engine has about 3,400 hours if you can believe the meters. If it’s a damper plate, what’s the harm in running it that way?.

kchace said:

How many hours on the damper plate? Those have a definite lifespan, are between the engine and transmission and can make quite a racket if one or more springs are broken. On the plus side they're pretty straightforward to change and not too expnsive.

Ken

Click to expand...

David

angus99 said:

Each engine has about 3,400 hours if you can believe the meters. If it’s a damper plate, what’s the harm in running it that way?.

Click to expand...

I suppose it depends on the type. Some fail open, meaning no go, some fail with just no damping meaning more wear on the transmission gears. Some fail into pieces and jam and stall the engine.

Of course it's anybody's guess even if you knew it was the damper - how much longer it may last.

Ken

Thank you, Kan and all.

I guess my real question is whether the noise is an indication of inevitable failure or “must repair”?

Edit: Oops, reading closer, I see you answered that.

Just hope it isn’t cylinder#6 scuffing. Much rather it be a damper plate.

My dampener went 100hrs and over 600 miles between first clacking sounds and failure to locking up the flywheel stalling the engine...15 miles from home but in some lousy sea conditions.

Hope to never repeat it.... An easy job if you have decent access at the rear of your engine.

psneeld said:

My dampener went 100hrs and over 600 miles between first clacking sounds and failure to locking up the flywheel stalling the engine...15 miles from home but in some lousy sea conditions.

Hope to never repeat it.... An easy job if you have decent access at the rear of your engine.

Click to expand...

Thanks, Scott. Please define “easy.”

Comodave said:

Just hope it isn’t cylinder#6 scuffing. Much rather it be a damper plate.

Click to expand...

Fingers and toes crossed.

Comodave said:

Just hope it isn’t cylinder#6 scuffing. Much rather it be a damper plate.

Click to expand...

The #6 scuffing is a 120 problem.

Just a lot of bolts to take off and put back....no adjustments really unless you feel the need to realign the engine afterwards.

As long as you can get there and slide the tranny back a few inches...and support it.

If your rear engine mounts are on the tranny, different story.

psneeld said:

Just a lot of bolts to take off and put back....no adjustments really unless you feel the need to realign the engine afterwards.

As long as you can get there and slide the tranny back a few inches...and support it.

If your rear engine mounts are on the tranny, different story.

Click to expand...

That doesn’t sound too bad. No mounts under the tranny and ample access (thank you, Art). Still, I’ll probably have a pro do it. Too many other chores and it would take me days to do something a pro could do in hours.

While I had my tranny off, I took it for a checkup, flush, new front and fear seals

angus99 said:

Each engine has about 3,400 hours if you can believe the meters. If it’s a damper plate, what’s the harm in running it that way?.

Click to expand...

The dampers on Lehmans are rated for 2,500 hours. If the springs break they can drop down in the housing and get jammed such that the engine actually is stopped. IMHO you need to have the dampers replaced in both engines. ANGUS, you know my boat. The repair records that came with the boat, although not complete, did not show that the plates were ever replaced, 5,500 hours on the clock. There was a lot of clattering at idle, an indication that the springs were weak and loose. No way way did I want to be doing "the loop" with those old damper plates. They both got replaced before we left. As I write, we are tied up in Smith Falls, Ontario on the Rideau Canal/ River. No more clattering by the way.

One significant omission in my earlier post: this engine had a Twin Disk transmission retrofitted after the Velvet Drive failed. The noise is not coming from the tranny, however, but from the bell housing of the engine. Does this change anyone’s diagnosis?

Anyone know any good diesel mechanics on the extreme upper eastern shore of the Chesapeake? (We’re at Worton Creek, but I don’t know what their availability is going to be.)

Amazing how something I never knew existed can wreck months of planning. I know . . . . plans . . .

kchace said:

How many hours on the damper plate? Those have a definite lifespan, are between the engine and transmission and can make quite a racket if one or more springs are broken. On the plus side they're pretty straightforward to change and not too expnsive.

Ken

Click to expand...

Will the boat have to be pulled? I imagine a fair amount of water gets in if the shafts have to be slid back.

No, shouldn't have to pull the boat, any shaft leaks should be minor if it can't be adjusted to none.

If your shafts can be slid back about 4" or so it's enough.

So the service manager here at Worton Creek just stopped by (on his day off; can’t say enough good things about John LeClair) and listened to it. He’s skeptical that it’s the damper plate. Thinks it might be a gear. They will tear into it first thing Monday and we’ll know for sure. While it’s open, I’ll probably have the damper replaced anyway—may even do the other one.

Can also be a chunk of carbon that gets loose on piston top then starts hitting bottom of cylinder head. Makes aggravated piston slap. Will tend to clear itself out with running.

You mention the noise faded after a restart, that sounds less like a damper as they do not heal.

Not sure what he meant by "gear noise".

Can you post a vid with sound?

Hope you can hear what I’m hearing. Not sure the sound went away when she revved it up; maybe just too much engine noise to hear it clearly? The “squeaking” noise is really more of a rattle.

Thank you yet again, Ski.

https://youtu.be/pTq9LZ-sNLM

Transmission

Which Model Twin Disc transmission do you have in your boat that replaced the Velvet Drive ?

Doesn't sound like a damper plate to me. The way it changes tone after a little rev, I'd put my money on Ski's prognosis.

When mine damper plate failed it was a more significant clacking noise, but barely noticeable at idle in nuetral. Much more pronounced in gear between idle and 1500 rpm.

alfamike said:

Which Model Twin Disc transmission do you have in your boat that replaced the Velvet Drive ?

Click to expand...

It’s an MG5011SC. I just changed the oil in it but noticed the noise beforehand.

If there’s a consensus that it’s not the damper plate, I wonder how to tell if it’s carbon, as Ski suggests, or a “gear noise” as the service manager hear believes. Also if it’s worth tearing into.

I also don’t know how strict that 2500 hour replacement recommendation actually is. Not trying to cheap out, but would love to know.

If your tranny comes off, it's easy to see the condition of the dampener plate and for around $200 in parts per engine might be worth doing anyway.

Bump . . .

. . . for any additional thoughts on the video.

https://youtu.be/pTq9LZ-sNLM

Thanks

"I wonder how to tell if it’s carbon,"

Getting rid of carbon in the cylinder head is simple.

After a run with the engine warm , use a "flit" gun a hand held insecticide pump from decades ago filled with tap water.

Idle the engine about 1200-1500 RPM and spray tap water in the intake with enough volume that the engine stumbles , but does not stop.

The water steam cleans the carbon out , on a vehicle a piece of newspaper behind the exhaust will show the results.

Doing this before the next oil change is quick and simple.