Cummins 480CE engine vibration

sailorjerry

sailorjerry

Member
Feb 12, 2011
185
Newport, RI
Boat Info
2003 Sundancer 460
Engines
Cummings 8.3 6CTA
Hey All,

I have a 2003 460DA with Cummins 480CE's aboard. I have put 800 hours on the engines in 12 months with no issues. Recently, when I run at about 2900 RPMs, I get a hard vibration and a drop in RPMs for 1-3 seconds, then it subsides. It then gets more frequent. If I continue, it can be almost a constant thing.

I ran an hour yesterday at 2200 RPMs with no hard vibration, but I can feel a small vibration with no RPM loss. I pushed it to 2900 just to see if it was still there and it happened again.

I have checked the wheels for obstructions, but found none. I did check the tranmission fluid level and it is good.

Thoughts?
 
Those engines are are rated for 2650 rpms....seem like you are running them on the high side. I have 480ce's and run them at 2100 - 2150.
 
There is a known problem of the damper separating from the coupler on C Series Cummins. You probably need to get a Sea Ray dealer or Cummins technician on the boat to be sure what is going on. One clue is black dust on the front of the transmission housing where it bolts to the engine. The black is the rubber disintegrating where the 2 parts of the flywheel are vulcanized together.
 
fwebster said:
There is a known problem of the damper separating from the coupler on C Series Cummins. You probably need to get a Sea Ray dealer or Cummins technician on the boat to be sure what is going on. One clue is black dust on the front of the transmission housing where it bolts to the engine. The black is the rubber disintegrating where the 2 parts of the flywheel are vulcanized together.
Click to expand...

Thnaks Frank. I will look for the dust and note this issue when I call the technician.
 
I have a 390MY with 480CE's on them. Not sure if your boat is in fresh water or not, but I would make sure there has not been any buildup on the props. That can definitely send a vibration through your boat. Also, depending on the size of your boat, there is a harmonic frequency at a certain RPM that will send shudders through your boat... kinda like a vibration. On my boat it is right around 1900 RPM... I tend to run mind right around 2000 RPM.

I would also check to see if you are getting any water in your bilge. That could mean you have a bit of a bent shaft and water is coming in past the seals. Hope this helps.
 
IMO, it could be a fuel related issue. Have you tried changing your fuel filters (primaries and racors)? How's the racor bowl looking? It could be just a bad fuel load.
 
It's just the way I read the OP's post. He gave us very little details, but stated that his running gear is fine. I'm just thinking that if an engine has fuel issue it might vibrate at different RPMs due to starvation (like a misfiring gas engine).

From my experience if a prop is damaged then the vibration is more noticeable when engine is loaded the most, which would be getting out of the hole. Unless we get more details from OP on running gear and/or other symptoms it won't be possible to determine the true cause, IMO.
 
Nope.......a diesel either fires or it doesn't. There isn't any misfiring. If filters are clogged, either the engines slows down, or it sucks air into the fuel system. If it sucks air in, cylinders don't get fuel because air is compressible so the injectors won't open.
 
fwebster said:
Nope.......a diesel either fires or it doesn't. There isn't any misfiring. If filters are clogged, either the engines slows down, or it sucks air into the fuel system. If it sucks air in, cylinders don't get fuel because air is compressible so the injectors won't open.
Click to expand...

I mentioned it only b/c I remember one time when I was changing primary filter on one side and didn't pre-filled it it took a while to pump with manual pump and then a lot more attempts to fire up the engine. When it finally fired up it was shaking for some time until the air was purged form the system. To help with purging air I've applied some extra throttle, but one thing I know for sure that the engine was shaking (sort of like misfiring gas engine).

I understand your point, but I think that it could be possible to have a scenario of some stuff at the bottom of the tank to stir up or just have a bad fuel to cause a slight "misfiring". Just a thought.

In regards to running gear, from my experience if there was some damage the vibration would be noticeable much sooner before you get to the optimum cruising RPMs of 2200-2300RPMs.

I think that at this point we need some more details from OP.
 
I know this is an old thread but was the problem ever resolved? figure out what the issue was?
 
You must log in or register to reply here.

Forum statistics

Threads
113,259
Messages
1,429,520
Members
61,136
Latest member
Gforce lll
Back
Top