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Old 02-21-2019, 01:04 PM   #21
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Have you looked at the aftercooler?
In 1500 hours, it might need service, though it’s not blowing black smoke.
Read up about that and on “low power troubleshooting “ at sbmar.com.
You noted that you hadn’t checked blowby, you might also want to look up crankcase oil level article, it’s common to overfill oil, and that will eventually plug up the aftercooler.
Another possibility is raw water intrusion from the exhaust side.
Almost forgot to mention the fuel shutoff valve. If it’s not fully opening, it will starve fuel supply.
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Old 02-21-2019, 01:13 PM   #22
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Have you looked at the aftercooler?
In 1500 hours, it might need service, though it’s not blowing black smoke.
Read up about that and on “low power troubleshooting “ at sbmar.com.
You noted that you hadn’t checked blowby, you might also want to look up crankcase oil level article, it’s common to overfill oil, and that will eventually plug up the aftercooler.
Another possibility is raw water intrusion from the exhaust side.
Almost forgot to mention the fuel shutoff valve. If it’s not fully opening, it will starve fuel supply.

Post #18...
"Aftercooler was serviced about 6 months ago and reported to be "in better condition than I have ever seen" as reported by the tech."..
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Old 02-21-2019, 02:08 PM   #23
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Post #18...
"Aftercooler was serviced about 6 months ago and reported to be "in better condition than I have ever seen" as reported by the tech."..
Thanks Smitty!

Kap, fuel shutoff valve. Hmmmmmm...I usually keegood track of those but I can say I haven't concsiously looked at them. I shall check. I could only wish it was that easy...
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Old 02-21-2019, 03:11 PM   #24
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Thanks Smitty!

Kap, fuel shutoff valve. Hmmmmmm...I usually keegood track of those but I can say I haven't concsiously looked at them. I shall check. I could only wish it was that easy...
Have you been able to rule out the aneroid or the boost going to the aneroid yet?
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Old 02-21-2019, 04:50 PM   #25
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Have you been able to rule out the aneroid or the boost going to the aneroid yet?
Not yet. Haven't been to boat. Not sure how to rule it out though...other than look for leaks.
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Old 02-21-2019, 06:12 PM   #26
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aneroid? Cool, never heard that before.
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Old 02-21-2019, 07:55 PM   #27
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Blessed are naturally-aspirated engines having less complication. Unfortunately, turbos are more common now due to air pollution requirements.
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Old 02-22-2019, 03:00 AM   #28
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Turbo lag

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In the first photo of the aneroid adjustment instructions in this link the boost pressure sensing tube is connected to the actuator just to the right and above the adjuster access cap. Follow this tube back to the intake manifold, looking for leaks , restrictions or kinks. Any delay in the aneroid control sensing the increasing boost would cause the symptom you see, the control would limit fuel rate until the pressure built up at the sensor. Perhaps remove the tube and blow it out to be sure it is not clogged.
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Old 02-22-2019, 08:13 AM   #29
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In the first photo of the aneroid adjustment instructions in this link the boost pressure sensing tube is connected to the actuator just to the right and above the adjuster access cap. Follow this tube back to the intake manifold, looking for leaks , restrictions or kinks. Any delay in the aneroid control sensing the increasing boost would cause the symptom you see, the control would limit fuel rate until the pressure built up at the sensor. Perhaps remove the tube and blow it out to be sure it is not clogged.
Yes - exactly . In that picture of a nice new engine you cannot easily see how the tube and fittings can get pinched and corrode over time, especially at the turbo side which is obscured. It does not take much of a pinch, blockage, or leak to make a difference in the transmitted boost. Hopefully it is easier to see in person and it is also somewhat obvious when you go looking for it.
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Old 02-22-2019, 09:15 AM   #30
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the boost reference tube gets filtered air from the intake side. its unlikely to be plugged up. but there is a real possibility of a rust hole. mechanical damage is unlikely unless someone has been doing work on the engine in that specific area. but even then those tube are usually pretty robust and would take a heck of impact to kink it.
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Old 02-22-2019, 09:27 AM   #31
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the boost reference tube gets filtered air from the intake side. its unlikely to be plugged up. but there is a real possibility of a rust hole. mechanical damage is unlikely unless someone has been doing work on the engine in that specific area. but even then those tube are usually pretty robust and would take a heck of impact to kink it.
"the boost reference tube gets filtered air from the intake side. its unlikely to be plugged up"
I have seen a couple of cases where the turbo shaft seals were losing oil a bit and also where the engine blowby was routed back into the air cleaner allowing some 'slop' of oil and water to enter the tube area.
YMMV
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Old 02-25-2019, 06:14 PM   #32
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Do you have electronic throttles?
Do you use them synchronised?
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Old 02-25-2019, 07:27 PM   #33
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No electronic throttles or Synchronizers. And thanks folks. I have not been able to get down there to troubleshoot. The weather here has been horrible...along with other things getting in the way. Hopefully get down there this week.
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Old 02-25-2019, 08:40 PM   #34
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Black smoke equals soot equals unburned fuel which the aforementioned turbo lag would actually replicate, which you do not have. If your Cummins engines have electronic controls (as opposed to the older mechanical injection pump) then they are programmed to ramp the fuel in proportion to the boost pressure to avoid the soot (emissions). I could be missing something here but I would recommend you determine whether your engines are the old mechanical fuel delivery type before you go possibly chasing your tail on an electronic sensor problem. If there is an electronic engine controller mounted on the side of the engine then someone with the Cummins software can go online and read every parameter that controller is looking at to decide how much fuel to feed.
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Old 02-25-2019, 08:48 PM   #35
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I could be missing something here but I would recommend you determine whether your engines are the old mechanical fuel delivery type before you go possibly chasing your tail on an electronic sensor problem.
You are definitely missing something. Cummins 330B is a mechanical engine. Maybe I should use the proper official name of 6BTA 5.9 M3...or something like that. The similar common rail electronically controlled engine nomenclature is QSB 5.9.

I am fairly well versed in the operation and mechanics of this engine. The one thing I have learned in this thread is the boost "sensor" going to the injection pump. I put "sensor" in quotes because it appears to be mechanical in operation with an aneroid sensing the boost pressure and adjusting fuel based on boost pressure as the engine comes up to speed.
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Old 02-25-2019, 09:51 PM   #36
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I did not see an indication of the age of your particular engines so I had no idea of the controls. I worked as a Cummins power tech on backup power systems till I retired in 2010 so I "assumed" they were equipped with the engine mounted ECM. My apologies for butting in.
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Old 02-25-2019, 09:56 PM   #37
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I did not see an indication of the age of your particular engines so I had no idea of the controls. I worked as a Cummins power tech on backup power systems till I retired in 2010 so I "assumed" they were equipped with the engine mounted ECM. My apologies for butting in.
No apology necessary and you certainly weren't butting in. My apologies for not being more clear! I think most of us have been onhere for quite awhile and have a good idea of the boats and engines we have. I see you are new...welcome aboard. And another apology if I came off as harsh or not very welcoming!! Stick around and have fun. Your expertise will be greatly appreciated!
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