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  1. #1

    Default 8V92 black smoke

    Hi all, First post from a newbie.

    I've got an old fibreglass Randell with a Detroit 8V92 550hp marine engine in it.

    It was running well until it sat in the harbour for around 8 months. I was running it on the mooring for a half hour here and there thinking i was doing the right thing. I've since been told these engines don't like being idled too much as it can gum up the injectors??? The fuel is old but i paid to have the fuel polished.

    I took it out for an overnighter recently. It wouldn't get up to 1500 revs while moving and when i pushed it, it would blow heavy black smoke.
    It does need an antifoul...

    I got it up to higher revs in neatral to see if that changed anything and it blew out a heap of black smook, soot. I limped it home. It still sounds nice and smooth, not running rough. Just won't get up to speed and blows black smoke. Doesn't get hot. The oil pressure alarm did come on a couple of times when i pushed it a little.

    I'm heading out to have a look at a few things.

    - check air filters. Take out filters and run to see if blows smoke
    - check engine bay vents are open and exhaust fan is running. (I don't think it was on last run)
    -should i attempt to clean injectors or should i look at putting an injector cleaner in???
    - check fuel filters?

    Any help much appreciated. I will get a mechanic to look at it but i'd like to check the obvious things first.

    thanks in advance

  2. #2
    Join Date
    Nov 2009
    temecula, ca., usa

    Default Re: 8V92 black smoke

    Black smoke is from excess fuel or a lack of air OR...a little of both. And, yes, a dirty bottom will put a heavy load on the engine and she will smoke if it drags her down too much.

    Checking air filters is a good idea in this instance. Also, the turbo charger should be looked at and boost pressure checked. The turbo shaft must spin very easily and there should be no "crunchyness" or "lumpiness" in the bearings. Check the oil supply line to the bearings for leaks or kinks and check that the turbo bearing oil drain back is clear and not sludged up. Turbo needs LOTS of FRESH, CLEAN oil for long life.

    Check blower air box drains frequently and keep them clear. If you're running an Air-Sep system, make sure it's working as it should. If the air box fills with oil, you will likely have EXPENSIVE problems.

    Good luck.

  3. #3

    Default Re: 8V92 black smoke

    Thanks very much for the reply. I'll be checking these things you have mentioned.

    Do I have to take both the turbos all the way off to check how smooth the shaft is spinning?

  4. #4
    Join Date
    Nov 2009
    temecula, ca., usa

    Default Re: 8V92 black smoke

    Turbochargers don't need to be removed for a cursory inspection. You can remove the intake ductwork or exhaust pipe and be able to look at the blades and spin the wheels.

    Turbos will usually fail the oil seal on the exhaust (turbine) side more frequently because of the heat. But oil seals on the compressor side can leak too.


    The turbochargers on this engine are EXTREMELY powerful and will suck in ANYTHING left near them....even at engine idle. Hammers, chisels, rags, wrenches and hands and arms are all things that big diesel turbos have been known to ingest when proper precautions are not observed.

    Another thing that people unfamiliar with the Detroit Diesel 2 stroke engines are surprised to learn is that it is recommended that you not use multi viscosity oil. The oil recommended is a single weight, usually 40, CD/CFII (CF2), low ash content motor oil. Although, as oil formulas increasingly improve, you will find owners running multi-vis oil in their 2 stroke diesels and reporting no problems. There was much debate about the subject a few years ago but, as far as I know, Detroit Diesel never waivered about the requirement to use single viscosity oil in their engines due to a host of factors. The main one being something called "viscosity shearing". Much can be read on the subject if you care to Google it.

    I see that there is an old thread here about black smoke on a vessel running 6 71 Detroit power and they talk about crankcase venting filters that they found clogged with sludge. These filters are described in the thread as being "add on" and I don't have any knowledge of them. But, you may want to read the posts because you're experiencing something similar.

    Good luck.

  5. #5

    Default Re: 8V92 black smoke

    Excellent information. Thanks very much.

    Will take it all on-board.

    I did read the thread on the crank case venting filters filled up with sludge. Not sure if mine has these but will be looking into that too.

    much appreciated.

  6. #6
    Join Date
    May 2015

    Default Re: 8V92 black smoke

    If you have a barnacle buildup on the prop you will get black smoke. It like trying to turn a bigger prop. The engine is controlled by the governor. When you move the throttle, your changing the governor setting. The governor will open the injectors to maintain the corresponding rpm, but bottom and prop fouling will keep the rpms down. Be careful of running the engine while overfueling. Especially with a twin turbo engine. High exhaust gas temperatures will eat away at cylinder parts - valves, rings, pistons and sleeves, greatly reducing engine life.
    A burnt injector tip can also cause black smoke. Don't remove the injectors unless you know how to reset them and set the rack.

  7. #7

    Default Re: 8V92 black smoke

    Thanks Lepke,

    It's definitely due for an anti foul so thanks for that tip.

    I won't be taking out the injectors to clean them without getting a mechanic on board to re install them. Thanks for the replies, i'm learning alot of these forums. #


  8. #8
    Join Date
    Apr 2013
    Lower Columbia River

    Default Re: 8V92 black smoke

    Many moons ago, my Dad had a boat powered by a 6-71. It had two fuel tanks and we would run off of only one at a time. One time we opened one tank's fuel supply valve, but did not open the fuel return valve. The engine blew loads of black smoke, and after a period of time blew out a flexible hose in the return line.

    I don't know if this scenario applies to your modern 8V92.

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