black smoke underload

[boatpoker]

ZeeHag, What is "rodlmffao".
thanks.

[boeing1]

I have checked fuel filters, air cleaner, and oil, flow from exhaust was normal. I have even added fuel injector cleaner to my fuel, thought it could not hurt... before going deeper into my engine, major surgery, I will have my bottom cleaned and recheck.
I think it is more unburnt fuel, witch could be bottom/prop dirty....
thanks for all the help, will post a update after bottom is cleaned.

[lonesoldier0408]

You didn't state how much duct work is involved in your air intake system. A bee nest in the wrong spot will cause the same air/fuel ratio issues. A shop towel sucked into an air filter housing. Dirt Dauber nests in the intake system. After years of driving trucks, a more gradual acceleration reduces black smoke, and improves mileage. And again anything to reduce drag. Is she riding lower in the water?
Not trying to reinvent the wheel, just food for thought..

[a64pilot]

If its from increased drag from a dirty prop or bottom, or from being over-propped the engine will not reach max RPM under full throttle, so if your reaching full RPM, then it's not from a dirty bottom.
To be fair most of the other causes, bad injectors / restricted airflow will cause you to not reach full RPM also.
ANY engine that is "making oil" is a problem that needs to be addressed, it's almost certainly fuel dilution. BTW fuel dilution or "making oil" is common on four stroke outboards that spend a lot of time trolling on fishing boats.

My belief is that Ultra Low Sulfur Diesel due to it's lower lubricity (believe it or not but that is a word) is causing premature wear on Diesel fuel injection systems, so your injection system may require more frequent overhaul than it used to.

[TeddyDiver]

Originally Posted by fstbttms

Black smoke is the most common, and it indicates that unburned fuel is being ejected with the exhaust gases.

Just for the record to get it right..
White smoke=unburned diesel
Black smoke=incomplete burning
Blue smoke=engine oil

[perchance]

Just to clarify, black smoke is caused by incomplete combustion whereas uncombusted diesel emits gray white smoke that lingers in the air.

[giant]

Originally Posted by boatpoker

ZeeHag, What is "rodlmffao".
thanks.

ROFLMAO. (Internet slang) rolling on the floor laughing my ass (or arse) of.

Just googled it.

[Andrew Troup]

zee

I'm sorry to say this but it seems to me your message about "these same lies" was inflammatory and unclear, and your subsequent crimes against logic just made it worse.

You are dancing on the head of a pin, I reckon, when you conflate excess fuel delivery caused by an external overload with excess fuel delivery caused by fuel delivery system defects.

And when both A and B can demonstrably result in outcome C, you cannot dismiss cause A by saying that in your experience and that of any number of others it has always been cause B.

[westwinds]

After checking for fouling of propeller and hull, I would check the injectors. Pull them and check for good spray pattern or just take them to a shop that does injection pump rebuild. It's also a good idea to have an extra injector and tools to remove if you are going to be away from a city that has a good shop. I like to pull the injectors at 1000 hours anyway as preventative maintenance.

[lockie]

hag, your use of the word "lies" is what's annoyed people.

The listed causes are real, and the most frequent, causes. Not being the ONLY ones doesn't make them lies.

You earnt the flaming!

lockie

[boatpoker]

Originally Posted by giant

ROFLMAO. (Internet slang) rolling on the floor laughing my ass (or arse) of.

Just googled it.

so is "RODLMFFAO" a mis-spell by Zeehag ? or ... is Zeehag being creative ?

[fstbttms]

Originally Posted by boatpoker

so is "RODLMFFAO" a mis-spell by Zeehag ? or ... is Zeehag being creative ?

My guess is the first five letters of her acronym stand for, "Rolling On Deck Laughing My..."

I have an idea what the rest of the letters stand for as well, but I don't want to be accused of beating up on a girl again, so I won't elaborate further.

[bobconnie]

Any smoke , white, grey, black, is wrong and if ya don't know the cause ya better get a diesel mech to ck your engine out !! A properly running diesel should have no immissions when running under load! And what is this stuff about Max RPMs? Ive kept my boats propped to run at the factory suggested running RPMs, never Max RPMs?? Have things changed?? I don't think so ! cus my engines run 5000 to 8000 hours with normal maintainece! And Ive had perkins with over 8000 hours that still did not smoke ! Maybe folks are reading things a little wrong maybe ???

[a64pilot]

Max RPM means that a lightly loaded boat running with a clean bottom and prop in no wind / current condition, the engine if run wide open should reach the maximum allowable RPM range. Not suggesting you should run one that way, but lugging most modern Diesels is bad for them. My experience with Diesels is they like to be run at 50% to 75% power, not higher or lower for extended periods

[jimbunyard]

To narrow down the possibilities, more information is needed:
Define heavy load
Did problem just start or has it been getting progressively worse?
Engine hours, make and HP
Is there a real air filter or is there just a silencer?

Certainly any of the things described above could be wrong, and it makes sense to do the least expensive first, but small diesel engines are inherently simple and it shouldn't be too hard to figure out what's wrong.

Typically, if all filters are clean and there are no intake or exhaust restrictions, and the engine and installation are mechanically sound, the first thing to check would be fouling, especially on the prop itself. It shouldn't hurt to add a high quality inj cleaner, but it shouldn't be necessary if filters are maintained and good fuel is used.

Having worked on both diesel and gas boat engines for years, I'm a little jaded and automatically assume that someone has an overpitched prop when I hear about black smoke. A good way to check for over-(or under for that matter)pitching (which may not help you at this point) is, with a clean hull and prop, underway with no head or tail wind or tide, at wide open throttle the engine should at least reach the manufacturers rated redline (preferably about 75-100 rpm more, to allow for future loading and fouling.) If it's more you're underpropped but that isn't quite as bad.

And by the way, black smoke is incompletely or inefficiently burned diesel, white smoke is unburned diesel (uh-oh), and blue is burning oil (soon to be uh-oh).

Of course, this leaves out any idiosyncrasies with your application, even an over-tightened stuffing box could push you over into black smoke mode in certain situations.