6CTA 8.3 Power Loss

[mooverfishing]

Hey Everyone, I have a 2003 8.3 6CTA 430HP.
Over the past weeks or so lost power and only turn 2275 WOT and slow acceleration No smoke, motor runs good, turbo boost is 20 psi, installed a vacuum gauge on rancor and there is 4-5lbs of vacuum on fuel side, not sure if that’s a problem? Any help would be great. Thank you

Topic

[Neto]

For what its worth, i have a 6CTA on a 21000 lbs vessel (Tiara 3500 express) and my props are  24x27x2 3 blade  #8 cup nibral. My vessel makes 2650 rpm full throttle

1 user thanked author for this post.

mooverfishing

[mooverfishing]

Hi Tony, thank you for your feedback.  Can you recommend a better prop? I know there are a lot of factors, I am currently running a 5 blade originally 30 pitch and 28 diameter now 28 pitch  x28.  Boat is about 19,000 pounds.

 

[Tony Athens]

Recommended was never 2600 RPM.. That is an absolute minimum RPM under worst case conditions as to weights, etc.. ..READ what CUMMINS says…………….   Recommended would be 2650+ RPM. ( same as the no-load RPM on a 480CE)  IMO, you still have your propping/engines loading not where it needs to be…………………………….But if you are happy, that matters too..   Tony    

[mooverfishing]

The Fix

Should of updated sooner- So we did figure out the problem in September when we had more time to examine closer. It was not getting WOT. It was  about 1 MM from getting WOT=about 125rpms believe it or not. Any way we did still do more prop work (5 Blade Prop) to get 2600rpms recommended. 

[mooverfishing]

Update on trouble shooting problem

OK so I pulled the boat recondition the prop, power washed and painted the bottom, as expected gained 125 rpms but only 2400, then replace the primer fuel pump which was leaking and still only turning 2400 at wot. Any suggestions?

[Tony Athens]

Replace it & “see”………..BTW, when chasing and issue like you describe, “almost” is not the right answer.

[Tony Athens]

#1——————Calibrate your tachs–The 480CE (if that what what you really have) will not go over 2650 or so in neutral

#2———–One engines tach seem right but the engine is GROSSLY over propped–This is one engine that will ot tolerate that with suffering major internal damage.

#3——Got any boost numbers at any RPM under load?

[Fred]

Same Problem 6CTA 480CE

I have the same problem.

Port engine is slower to accelerate and only gets 2400 rpm WOT in gear and about 2660 in Neutral.
It basically needs a little time at 1500 before it will continue to accelerate.

Starboard gets close to 2700 in gear and 2900 in neutral. No lag at 1500.

These numbers are all after replacing fuel filter last and snugging up the lines. It helped a lot and got the acceleration time better. The filters were not very dirty so I am thinking the lines might have had a small air leak. I have also checked around turbo to make sure everything is tight.

So what do you recommend next? Testing lift pump fuel pressure? Being that I have the electronic fuel controller there is not much to play with there. Should I swap sides? I might also blow the pickup lines to make sure there is no crud that restricts.

After cooler serviced less than 3 years ago. 130 hrs ago. And I have put 100 hrs on it last year.

I have no fuel flow gauges.

Any ideas?

-Fred

[mooverfishing]

Leaking fuel primer

Ok so Machanic found the Primer / fuel lift pump is leaking fuel and air when you push on it . Could this be my problem?

[mooverfishing]

Hey Tony, my Machanic was working on boat today and found the primer was leaking fuel and a lot of blow bye when he pressed it in. Could this be my problem? If so I’ll order the parts from you.

[mooverfishing]

Got it thanks

[Tony Athens]

Cummins Bosch P7100 Injection Pump Throttle Arm Adjustment

How the Cummins Bosch P7100 Injection Pump Solenoid Works

Learn “tony’s tips”– It’s all there

[mooverfishing]

Hi Tony,

I bought boat in October with 600hrs, I have over 1200 hrs now, no history of maintenance except what I have done, replaced after cooler and hoses, all fuel filters, I don’t run it hard but maybe a month or so ago I noticed loss of power.

Throttle is almost at 100% it’s just a tiny it from full and no I did not check injection pump lever, where is it located?

2200 speed I think is same or maybe a little less, I have. Of owned it long so can’t remember exactly.

[Tony Athens]

Post a timeline history of the power loss and engine maintenance history in general.

Last time engine made over 2600RPM in gear loaded as you use the boat?

Making 100% full mechanical throttle? You have visually checked at the injection pump lever??

Vessel speed now at 2200RPM vs vessel speed before at 2200RPM?

Answer the above as asked

[Author]

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