Cummings 6CTA 8.3

Blown284

Blown284

Well-Known Member
Jan 12, 2014
1,122
Chesapeake Bay
Boat Info
2004 SeaRay Sundancer 460
Engines
Cummings 480CE
HI folks. I made an offer on a 460 sundancer which has the Cummings 6CTA 8.3 (480hp) engines in it. When doing some looking around/digging and research, I believe that what I've read is that these engines should be hitting approx 2650/2700rpm.

When speaking to the owner, he was able to get his boat up to 2500rpm (both engines) and said that his "cummings" mechanic indicated that perhaps one of the sensors wasn't allowing the engines to achieve full WOT.

I'd love your thoughts as I don't want to purchase a boat with potential issues. Could this issue be related to:

(a) fouled bottom
(b) lack of boost
(c) or something else?

I'm trying to educate myself as best as I can.

Thoughts? Comments?

Thank you,
Tim
 
Go to www.sbmar.com. Tony Athens is the guru of Cummins and has a ton of information on all things Cummins.

Generally speaking if the boat can not reach WOT + 50-75 RPM (Tony has some more specific requirements depending on the model/year engine) are overloading the engines, and need to reduce the load.

Reducing the load means a cleaner bottom, less fuel, less people, less stuff on board, or less pitch in the props, or a combination of things.

Failure to reduce the load is BAD. Things run hotter than they are intended and things go BOOM...Read $$$$$$$.

Don’t rely on the owners opinion...get a qualified Cummins mechanic to the boat to survey and Sea Trial the engines. That is separate from the hull survey.
 
Yes, understand. I have a cummings specialist that's going to be there. Again, just trying to educate myself. The engine person is separate from survey. Will be doing oil samples for genny, trans, engines, etc.
 
You need to do a lot of reading here and especially on sbmar.com . These engines have a history of problems when run over propped which your's are if they can only hit 2500. Be sure to get a Cummins engine surveyor to check these engines before you close.
 
Your engines are the 480CE. They need to be propped to match the desired fuel burn of the 450 Diamond (430hp predecessor to your engine). They are also at risk to dropping a valve when overpropped. There is also an improved head that reduces the risk of that valve drop problem. As others have written, you can read all about it on Tonys site. And or google "480CE valve drop"
 
ZZ13 said:
Your engines are the 480CE. They need to be propped to match the desired fuel burn of the 450 Diamond (430hp predecessor to your engine). They are also at risk to dropping a valve when overpropped. There is also an improved head that reduces the risk of that valve drop problem. As others have written, you can read all about it on Tonys site. And or google "480CE valve drop"
Click to expand...

I started to read all those documents. Based on what I've read, I need to get the props with more cup and get it in the range he suggests 13.6gph. Got it.

I just wasn't sure if there was something else I need to be concerned about.
 
Blown284 said:
I started to read all those documents. Based on what I've read, I need to get the props with more cup and get it in the range he suggests 13.6gph. Got it.

I just wasn't sure if there was something else I need to be concerned about.
Click to expand...
Yup. 13.6gph at 2200 rpm.
 
ZZ13 said:
Yup. 13.6gph at 2200 rpm.
Click to expand...
yep, roger that. I know there's a spare set of props. I'll do some reading to see what props are on it and figure out what is really needed. Boat is really heavy with hydraulic platform and such.
 
Maybe doesn't need to be said but.....have the cummins guy get in the bilge with photo tach to verify WOT rpm with engine sync off.
 
Woody said:
Maybe doesn't need to be said but.....have the cummins guy get in the bilge with photo tach to verify WOT rpm with engine sync off.
Click to expand...
My Cummins tech went down there during survey at WOT.... lifting the hatch it was insanely loud.... he had a big smile on his face going down the ladder like he was going home.... it was hilarious
 
Blueone said:
My Cummins tech went down there during survey at WOT.... lifting the hatch it was insanely loud.... he had a big smile on his face going down the ladder like he was going home.... it was hilarious
Click to expand...

LOL. Don't jinx me.
 
Your 480CE's are electronically limited to approximately 2680 rpm. They should easily reach that while the boat is fully loaded. Anything short of that is a problem. Sea Ray over propped these boats, so that's the likely issue should you fall short of that rpm.
 
What kind of time is on the engines? Look to see how toasty the out let of the turbo to the aftercooler looks. If it is bright white or at least not turd brown the engine may not have been overloaded on a regular basis. It would be great if you could get an idea as to the way the boat was operated. Did it cruise around at hull speed or was it run regularly at 20 kts. A friend of mine bought a clean pedigree 420SD with the 480SE and he dropped a valve on his first cruise. Cost him $32,000 to repair the one engine and upgrade the head on the other one. I would be very leery of this boat unless you can be assured somehow that the engines have not been overloaded over the life of the boat. It will be a ticking time bomb.
Carpe Diem
 
Carpediem44DB said:
What kind of time is on the engines? Look to see how toasty the out let of the turbo to the aftercooler looks. If it is bright white or at least not turd brown the engine may not have been overloaded on a regular basis. It would be great if you could get an idea as to the way the boat was operated. Did it cruise around at hull speed or was it run regularly at 20 kts. A friend of mine bought a clean pedigree 420SD with the 480SE and he dropped a valve on his first cruise. Cost him $32,000 to repair the one engine and upgrade the head on the other one. I would be very leery of this boat unless you can be assured somehow that the engines have not been overloaded over the life of the boat. It will be a ticking time bomb.
Carpe Diem
Click to expand...

860 hours. Just had service done (aftercoolers and such).
 
fr8dog said:
Your 480CE's are electronically limited to approximately 2680 rpm. They should easily reach that while the boat is fully loaded. Anything short of that is a problem. Sea Ray over propped these boats, so that's the likely issue should you fall short of that rpm.
Click to expand...

Got it. thank you.
 
Check to be sure the control cables are pushing the throttle levers to the stops.
 
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