Black Smoke

[edbulmer]

I have twin 3116 cats and when I take a trip on the boat the back gets covered in black. Seems like there is a lot of unburned fuel coming out. Is this normal with these engines or could an adjustment be made

[TeddyDiver]

Black smoke indicates overloading the engine..

[Target9000]

Clean your props.

[River Cruiser]

Originally Posted by TeddyDiver

Black smoke indicates overloading the engine..

+1, dirty hull, dirty air filters or over propped would be what I would check 1st.


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[edbulmer]

Just had the props and bottom cleaned, and had the props reconditioned (whatever that is) cause the marina guys said I needed it-(they say they saw bubbles behind the props. I don't even own a bubble maker. It cost $14.0000bucks, the diesel expert said I should run them around 2400 and that's what I do unless I'm on the intercoastal I cruise at 6 knots. I also see some smoke coming out even when in neutral, don't think that the engines are overloaded at that point. (Maybe someone is running a smoke machine down below)

[River Cruiser]

Are you able to reach your specified wide open throttle rpm?


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[Sailmonkey]

You may also have lots of carbon in the injector tips or weak injector springs causing poor atomization an incomplete fuel burn.

How many hours are on your injectors?

How hard do you normally run your engines (as a percent of load)?


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[edbulmer]

It was suggested I run them at 2400 rpms. I could back that off and run around 1800. 1200 hours on the motors.

[River Cruiser]

I do not know what the WOT rpm should be on your 3116 Cats, you can contact a Cat dealer with the model, serial number and arrangement number and they will give you the specified rpm. With a clean bottom and boat loaded how you normally use it and engines in proper tune you should be able to reach that rpm. You need make sure your tachs are correct before doing any other test, you can use a photo tach to make that comparison. Do you have boost gauges and exhaust gas pyrometers? These will help in determining engine load and condition. With the hours on yours there should have been a 1000 hour service performed recently by a Cat dealer mechanic. A dealer can check the records and tell you if this has been done, if it hasn't I would have them do it because of the special tools needed to set the injectors.


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[edbulmer]

Ah,, I bet that's the problem. I'll have the injectors looked into.

[Onoboater]

Happened on my neighbors Yanmar 2 Cylinder just recently. Black exaust. Could only get about 60% RPM. The engine kill lever was not going all the way down.

[Aloha_float]

Run some injector cleaner through the system as a first attempt to clean up your injectors.


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[TeddyDiver]

If there's any issue with the injectors (or timing) it should be noticeable whatever the rpm or loading happens to be, thou with a big difference with the amount of smoking. Normally in this case it's also unburned ie grey smoke rather than incompletely burned ie black smoke which is due overloading.

More smokes.. and propable causes..
Blueish smoke, burning engine oil, piston rings or valves
White smoke, water, head gasket