480CE Issues

Bigolie

New Member
Jan 26, 2023
8
Boat Info
2007 40 Motor Yacht
Engines
Cummins QSB 5.9
I'm interested in a 2005 Sea Ray 390 Motor yacht with 6cta8.3 480CE engines. I have read all the posts regarding the dropped value issue and the problem with the heads. I spoke to Cummins about this issue and gave them the serial numbers for the engines and the heads on this particular vessel. They advised me that there are no recalls or service bulletins for those engine or head serial numbers, and I shouldn't be worried about them if they have had proper maintenance and up keep. Does this sound correct?? From what I read, it appeared this was an issue with all Sea Rays with the 480ce engines and the only way to be sure of not having a failure was to prop to the 450 Diamond curve and to change out the heads. Based on what Cummins told me, it appears from their point of view, this is not an issue for all 480ce's, but only the ones with certain heads with the part numbers contained in the Service Bulletin. Any input regarding this issue and the 480ce in general, would be greatly appreciated.
 
I had a 2005 Searay with 480 CE's that dropped a valve and a friend had a 2004 Tiara that dropped a valve too. It is all about propping the boat to match the Cummins fuel curve. I did a lot of research and proved the results to myself by adding EGT gauges. Before removing 2 inches of pitch, exhaust temps were 900 and above at cruise. After the prop work the cruise temps were 700-750.
If the boat of interest has chocolate brown after coolers and pipes from the turbos it is over propped and living on borrowed time.

What Cummins told you is correct. If they have been run inside the prop curve and maintained they are fine. Few have been.

If you have not found Seaboard Marine yet check them out. There is a ton of info there on these engines. sbmar.com
 
How do you know if the boat is propped correctly, is it by engine temp and GPH at cruise under load?
 
How do you know if the boat is propped correctly, is it by engine temp and GPH at cruise under load?
On the sbmar.com site you will find a fuel curve Tony recommends for this engine. If you burn more fuel at the RPMs in the curve your over propped. Ideally you want to be on or just under the curve at cruise RPM ranges.

One caveat is to make sure that the rpm gauge is accurate, it's not always.
 
How do you know if the boat is propped correctly, is it by engine temp and GPH at cruise under load?

A quick test is also to see if you exceed the rated rpm at full throttle. If you can't your over propped. Same as above, can only be done with accurate rpm readings.
 
A quick test is also to see if you exceed the rated rpm at full throttle. If you can't your over propped. Same as above, can only be done with accurate rpm readings.

The 480CE's are rev limited by the ECM. 2680 is the limit. You should be able to reach that though. The fuel flow curve is the best way to tell where you are.
 
Really appreciate all the information!
 
I would like to add when you are checking your fuel burn with the curve my experience has been you may not get your boat to match the curve at all RPM's. You want to match where you plan to run the boat and not be too concerned with lower RPM ranges where the boat is not over the hump yet.
 

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