'99 380D CAT 3116's vibration?

LaPlaya

New Member
Jul 30, 2009
11
Seattle, WA
Boat Info
1999 Sea Ray 380D Sundancer
Engines
CAT 3116 Diesels
Have you experienced any vibration from the engine/transmission on the Sea Ray Sundancer 380D CAT 3116's? I'm still getting use to having diesels (love them) and at times I get this "feeling" that there is more vibration at idle/low speed coming from my port side... my wife thinks I'm nuts when I point it out, as an example, we were moving along at about 7 knots coming through a no wake zone area of the lake and I felt there was more vibration than normal based on a "rattling" I was hearing from my boarding doorway and when I looked at a bottle of water on my dash I could see the "vibration". I put the port engine in neutral and shut it off to see if it went away and although it wasn't as much with just the starboard engine running, it was still "just barely there"... when I did the same test by shutting down the starboard engine and just running the port engine, there is just a little more "vibration"...

I read there may be something about the port engine turning the prop counter rotation vs the starboard? Something to do with why the port engine consumes a little more fuel than the starboard? ... but from the thread I was wondering if this could be the vibration I sense at times?

Do you think there is a "normal" amount of vibration with these diesels/transmission? OR should they be really smooth with zero vibration?
 
I posted the exact same question when I bought my 400DA with 3116s. Basically it just rattles and vibrates when at idle. My boat was idling way too low which made it much worse. The idle should be adjusted to 750 rpm with no load. Once I set the idle correctly the vibration diminished a lot. I'm thinking that the old rubber in the engine mounts just don't isolate the vibes like they should, but I'm too cheap and lazy to replace all the motor mounts.

Should you decide to adjust the idle here are some instructions that Frank Webster sent me a long time ago.

3116 Idle Adjustment


3116/3126 MUI engines should idle no less than 700 RPM, 750 is better.


The idle adjustment is a screw recessed into the side of the governor. This is just an idle screw, not a valve that is open or closed. The engine should be at operating temperature before adjusting idle speed. Disconnect the throttle linkage to make sure the governor lever is free. Back out the idle screw in the side of the governor about 3 rounds. Adjust the throttle stop to 700 RPM, then raise the idle to 725 with the screw in the side of the governor. The engine should be smooth.


You should also check the dashpot orifice. This is under the small plate on the rear of the governor, attached with 3 allen screws (4 mm head). Remove the plate and locate the orifice in the spring housing. Use a 2.5MM allen wrench to make sure the orifice is tight. It should bottom in the housing by hand. You can remove the orifice and apply a small drop of blue lock-tite and then reinstall. You´ll need a new seal for the plate.

Good luck!

Pete
 
Thanks Pete, I've adjusted my Port idle to 750 RPM as it was about 710... That helped.

But I still feel that the Port side CAT 3116/ZF Transmission or it's alignment, or maybe the cutless bearing? Or propeller or shaft? I don't know. It has this THRUM THRUM THRUM sound that the Starboard side doesn't have... :)

Ideas?
 
Thrum Thrum Thrum. Dig it! Mine ( Cummins 6BTA 5.9's) starboard does it. Vibrates badly. port smooth as a new Singer sewing machine. I'm thinking on first checking alignment. Then go from there if that doesn't correct it
 
Frank Webster helped me once again. I'm still getting use to the sound of my diesels. He pointed out how diesels can sound off each other when they are not in perfect Sync, especially at low RPM where you can hear them and while you pay more attention. At that moment, a slight difference in throttle, and for mine I mean a very slight difference, causes the THRUM, THRUM, THRUM... Now when I hear it (sense it?) I make a very slight adjustment to one or both engines to tighten their sync and it goes away!
 

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