New vibration

Good morning. We experienced a new vibration yesterday. My question is can out of adjustment valves cause extreme vibration at higher rpms? Have never adjusted the valves but runs fine. It sounded like chain sliding in the locker but unfortunately wasn’t. It comes and goes but more at cruising rpm. Almost sounds like valves clattering? Is this a thing in the 120 Lehman? No changes in oil pressure or power. Kind of lost here. I’m gonna to do a thorough inspection today but in the water so can’t check outside prop or bearings. Any help appreciated. Terry

If it's the valve adjustment, it's probably in 1 or 2 cylinders and would have to be way out of adjustment. Valves need to be routinely checked and adjusted because the valve stem and the rocker pressing against it wear. When the clearance gets too big, they wear faster, eventually damaging the parts beyond repair. It can damage anything in the valve train, even the cam or the gear driving it. Out of adjustment valve clearances make a louder ticking noise.

You should check the motor mounts with the engine running, in gear, for any movement. Or with the engine off, use a long pry bar try to move the engine and mounts. Inspect the shaft, coupler and any bearings for movement. Make sure the coupler bolts are tight. Turn the propeller shaft by hand and feel for any tight spots in a 360° rotation.
Often a sudden addition of vibration is something on the prop. Usually a line, but even something organic like kelp can hold on a long time.

Something that causes all kinds of racket and symptoms is a failing dampner plate. When all else checks out....listen at the bellhousing, look for rust bits of metal under it, you can pull the starter and try to look for metal in the housing, even drill a small hole and use a boroscope to inspect.

This comes and goes so probably not valve train? Maybe picked something up outside. Boats in n the water for now. It’s very loud when it comes on and then it’s gone. Weird. Thanks I appreciate your input

Same thing with my dampner plate....on and off for a couple days with hellacious racket. then nothing for 500 Mile's, then totally locked up the engine.

We were in the TSW a few years ago. Went through a small lake with heavy weeds. I backed down several times and still had a vibration. When we went over the Big Chute railway the lockmaster went under the boat and pulled a bunch or weeds off the prop shaft. Vibration solved.

Damper plates do come in many grades OEM is usually not the finest.

If it's a loud noise, then not the valve train. I also think damper.

Ken

Thanks

On my way today or tomorrow but certainly appreciate each of you sharing with me.

psneeld said:

Something that causes all kinds of racket and symptoms is a failing dampner plate. When all else checks out....listen at the bellhousing, look for rust bits of metal under it, you can pull the starter and try to look for metal in the housing, even drill a small hole and use a boroscope to inspect.

Click to expand...

What he said plus the dampener plate is a maintenance item. I don’t remember the hours that it should be changed but if it fails, you are dead in the water. It took about 6 man hours to change ours.

So pull the boat then the shaft,transmission and then the plate rite? Thanks for responding.

mizzkim said:

So pull the boat then the shaft,transmission and then the plate rite? Thanks for responding.

Click to expand...

You can do it in the water as long as you can push the shaft rearward enough for the transmissions to pull out. You have to clear the hole in the dampener plate with the transmissions splined shaft.

You may have to rig something to support the engine if the rear motor mounts are on the transmission.

Thanks a bunch. That’s gonna save a load and f money.

Unreliable memory says damper plates last about 2500 hours before needing replacement.

BruceK said:

Unreliable memory says damper plates last about 2500 hours before needing replacement.

Click to expand...

LOL
They last as long as they last.
Mine are now at 7000 hrs roughly. and still going strong.

Solved. Perhaps.

mizzkim said:

Good morning. We experienced a new vibration yesterday. My question is can out of adjustment valves cause extreme vibration at higher rpms? Have never adjusted the valves but runs fine. It sounded like chain sliding in the locker but unfortunately wasn’t. It comes and goes but more at cruising rpm. Almost sounds like valves clattering? Is this a thing in the 120 Lehman? No changes in oil pressure or power. Kind of lost here. I’m gonna to do a thorough inspection today but in the water so can’t check outside prop or bearings. Any help appreciated. Terry

Click to expand...

After a trip with the shaft and prop to the machine shop for-rebalance and straightening plus a new cutlass bearing we seem to have solved our vibration issues. According to superior machine in anchorage Alaska the shaft was out of balance as well as the prop. Add in a little wear in the cutlass bearing and boom; vibration. I’ve never hit anything with it so it was surprising but apparently not uncommon. Also changed the dampener plate but the old one was good. O well you can’t have enough spare stuff for the old girl. Thanks for each response.

koliver said:

LOL
They last as long as they last.
Mine are now at 7000 hrs roughly. and still going strong.

Click to expand...

I was told by American Diesel that the Dampner Plates had a 2500hr change (obviously not hard and fast).


How can one tell their dampner plates are still going strong?

I ran into an increased noise recently too and mentioned it here. Guess's were also the damper plate. Had my mech come down and listen, noise was minimal from eng or trans. However there is a shaft bearing near the stuffing box that he figures is the culprit. When he can free up some time he is going to come work on it.
Do you have a shaft bearing on yours?

I have been wondering that myself. I am pulling my port engine this winter in order to replace the port fuel tank and that would be an easy time to replace the damper plate.

It most certainly is NOT the valves. Long story short, The front 2 valves (4 rockers) were so worn on my F.L.120 that the push rods actually fell out from under the rockers. Engine still ran, actually quite well but it was "backfiring" through the air intake, very loudly, sounded like a gun going off. Didn't even notice it from the flybridge until we slowed way down to make the dock.

It actually happened two times before the problem was finally fixed properly (engine rebuild) . The only sign we picked up was a kind of helicopter (whop, whop, whop) sound similar to what you often hear when a "go fast" boat is overtaking you. Good oil pressure, no vibration and still running pretty well. (didn't want to idle very well).

pete

In August I docked my boat with all gauges running normal, all sounds were normal, no indications of any problems. Two weeks later went to start engines and starboard immediately stopped solid. Starter would not move it. Checked fluids and coolant was down (later checked 1 quart).
Twins v. single? LOL. I completed my summer cruise plans on port only.
Friday with trans removed the problem became obvious. Two damper springs were awol, wedged between the housing and flywheel. No warnings.
Parts will be ordered and both engines will have new dampers installed.

Just a thought....it was recommended to me while I had the tranny off and it hadn't been serviced in awhile...to have it looked at and seals replaced.

psneeld said:

Just a thought....it was recommended to me while I had the tranny off and it hadn't been serviced in awhile...to have it looked at and seals replaced.

Click to expand...

Good advice if you are paying someone to do the work.