Cummins 6CTA 8.3 Loss of Power

Blue Chip

Blue Chip

Member
May 9, 2019
84
New Smyrna Beach, FL
Boat Info
2003 Sea Ray Sundancer 420
"Day Five"
Engines
6CTA 8.3M 3
Out for a ride on Sunday - nice cruise at 2100 RPM for an hour or so - sudden loss of power on the starboard motor. I could run it up to about 1500 RPM or so - but that's it. No smoke, no sputtering, no alarms, ran fine at idle - just couldn't get it past. When we anchored - I checked the wheels to see if I picked something up - nothing.

Any ideas? I had read that potentially a sensor could have gone out - causing the motor to limit itself...
 
There is no computer on your engine. Totally mechanical. They only thing restricting power would be air or fuel supply restriction. Air restriction shows up as black smoke (unburned fuel). Thoroughly check out your fuel path from Racor filters, to on engine fuel filter to lift pump to injectors.
 
I had a similar problem last year, albeit on a QSB engine. Turned out to be a loose bracket that caused the turbo fan to slip and restrict its airflow. No engine faults so it was frustrating but the marina tech found it pretty quickly.
 
Blue Chip said:
Is there anything that would limit the RPM of the motor - something like a sensor that went bad?
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ZZ13 said:
There is no computer on your engine. Totally mechanical. They only thing restricting power would be air or fuel supply restriction. Air restriction shows up as black smoke (unburned fuel). Thoroughly check out your fuel path from Racor filters, to on engine fuel filter to lift pump to injectors.
Click to expand...
 
No sensors. I had this happen once and it was the hose off the turbo. Check those hose clamps all the way to the aftercooler and then the same ones out of the aftercooler.

most likely it’s those or your turbo is bad.

see if it will spool up to 2900 rpm in neutral in the slip but... make sure the engine oil is totally warm before you do this test
 
+1 on all hose & clamps going from turbo to aftercooler to the engine. I had a clamp break and caused same issue. $8 fix.
 
Confirm throttle is hitting the high speed stop screw on the injection pump and that the fuel supply pressure to the injection pump is good under load. No smoke means lack of fuel on these engines. Faulty lift pumps are common. If supply pressure is good, 2 other components to limit fuel delivery and common to fail are diaphragms in the aneroid and/or waste gate actuator. They are both serviceable and can be tested with vacuum.
 
Circling back up on this - changed filters - Racor's and secondaries. Problem gone. The Racor's were nasty. As a side note - one gallon of diesel is not enough if you empty the bowls. Need about 2 gallons of clean diesel. I managed to get most of the air out of the system - so the restart wasnt bad on either motor.
 
alnav said:
I had a similar problem last year, albeit on a QSB engine. Turned out to be a loose bracket that caused the turbo fan to slip and restrict its airflow. No engine faults so it was frustrating but the marina tech found it pretty quickly.
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Al - what's the name of your Marina Tech? Always like to know about good diesel mechanics in our area..
 
NotHerDecision said:
That probably means you need to treat your fuel. I would recommend Frank’s fuel management article on the homepage.
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Thank you. I became a supporting member today and gained access. Very good article. I ordered the biocide for a shock treatment - as well as the other.
 
villain style said:
Al - what's the name of your Marina Tech? Always like to know about good diesel mechanics in our area..
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Mark, it was a shop tech at Clarks Landing, Shady Side; they've got several good guys. I've been very pleased with their work and the prices seem to be reasonable compared to other Sea Ray dealers where I have had work done. They are less than a mile from where I keep my boat so minimal travel charges for me. I will also drive the boat over there and leave it for major planned maintenance, this way I know I will get attention and no travel charges. I think like most other shops, they seem to be constantly busy and can be slow to respond to routine issues with the travel team. But, they jumped right on my engine problem last year.
 
Might want to get several sets of Racor filters...if you have crud in the tanks it’s going to take several filters before everything gets cleaned up, or if bad enough, have your fuel polished.
 
dtfeld said:
Might want to get several sets of Racor filters...if you have crud in the tanks it’s going to take several filters before everything gets cleaned up, or if bad enough, have your fuel polished.
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Agreed. Being new to the diesel world - I may be over reacting - but regardless - if the filter was clogged badly enough to block fuel flow - it was still nasty. The X factor here is that I don't know when the last time it was changed... building my own service log book now... I have a few sets - they are cheap enough and easy enough to do that it makes sense until I'm confident that it's handled.
 
Welcome to diesel ownership!! Fuel management is one of the new (but easy) tasks , just follow Franks guide, and you'll do great.

Check your fuel caps o-rings and replace to help keep water from getting into the tanks (this goes for all deck fittings). Water is an essential ingredient for "slime" growth and cutting down and eliminating water helps keep the tanks clean. Some gets in via the vent air, nothing you can do about that, but the cap o-ring deteriorate, and are often overlooked.
 
About 1.5 hours away from the 5 hour mark since doing the shock treatment and replacing the Racors and secondaries again... running great so far. Between the shock and the treatment - I should be good after this filter change.
 
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