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  1. #1

    Default 6-71 TI Smoke At idle

    I recently purchased a boat with 6-71 TI's the port engine smokes on start up and idle
    and seems to clear up as you throttle up I had a mechanic inspect the engines before I
    purcahsed the boat and was told it was an injector however we replaced 3 out of 6 and
    the problem is still there and am now being told it could be the intercooler is clogged up
    I do not believe this is water due to the oder could this be a compression issue ?

  2. #2
    Join Date
    Sep 2010
    Location
    Jersey Shore
    Posts
    4,567

    Default Re: 6-71 TI Smoke At idle

    You have to clean those intercoolers on a yearly basis.

    Does the engine that is smoking fire right up or does it require extended cranking or starting fluid?

  3. #3

    Default Re: 6-71 TI Smoke At idle

    If the block heaters are not pluged in it starts up after 2-3 cranks but if it is cold it is difficult

  4. #4
    Join Date
    Sep 2010
    Location
    Jersey Shore
    Posts
    4,567

    Default Re: 6-71 TI Smoke At idle

    What is the outside air temp where the boat is. If the temp is above 50 degrees and you need the block heater to start, it may be time to do a cold compression check of that engine. Low compression makes them a bear to start when the temp drops. And they smoke like crazy.

    You can remove the inspection plates on the side of the engine and look at the rings for cracks.

  5. #5

    Default Re: 6-71 TI Smoke At idle

    We are in NY and the boat was in the water all winter so it has been pretty cold if the rings
    were cracked wouldn't the engine smoke all the time?

  6. #6
    Join Date
    Sep 2001
    Posts
    434

    Default Re: 6-71 TI Smoke At idle

    engine smokes at idle, and clears up is caused from cold stuck rings. best way to fix is to run under load, it will clear up after a few hard runs.

  7. #7

    Default Re: 6-71 TI Smoke At idle

    The smoke clears up when you raise the throttle even when docked the mecahnic that did the survey initialy tod me it was a bad injector dripping fuel at ldle and burning it off as you increase the RPM

  8. #8
    Join Date
    Nov 2009
    Location
    temecula, ca., usa
    Posts
    2,614

    Default Re: 6-71 TI Smoke At idle

    Here's the "smoke" chart:

    Blueish or blue gray=lube oil being burned=piston oil control failing or valve guides worn or both.

    Black=over fueling or lack of adequate air to burn fuel entering cylinder. Usual suspects are clogged, collapsed air filters, inadequate turbo boost, wrong injectors, poorly timed injectors, faulty governor, disabled smoke control device or engine overloaded.

    White...Not really smoke but unburned, vaporized fuel "fog" that hangs in the air with a strong fuel smell=not enough heat in cylinder to even partially ignite the fuel. Indicates loss of compression in one or more cylinders.

    Steam...dissipates quickly in surrounding air. Indicative of an internal coolant leak to combustion chamber due to head gasket, cracked head, leaking intercooler or aftercooler.

    You didn't actually say white smoke but from your description that is what I am guessing. If it were a "drooling" injector, you would get black smoke. My guess is that you are dealing with a bit of poor ring seal on cold start and not cracked rings as it clears right up. Not terribly unusual on a Detroit with a "few" hours on it. Time to find another mechanic for reliable advice.

    Good luck.

  9. #9

    Default Re: 6-71 TI Smoke At idle

    Thank You unfourntunatley you confimed what I thought it may be but from what I have been told you can change out the rings without removing the engine.

  10. #10
    Join Date
    Dec 2008
    Location
    Baltimore, MD
    Posts
    21

    Default Re: 6-71 TI Smoke At idle

    I had a similar problem a couple years ago on one of my 671s. Swapped out an injector - it still smoked at idle, even after running under a load for an hour. Did compression check - all cylinders in the 475 psi range...Mechanic didn't have an explanation. Then after a one hour cruise, I brought it back to idle speed and noticed the temp gauge was around 115 degrees (it was very early spring). Opened thermostat housing and found a piece of trash holding stat wide open, so engine was running too cold - and they will definitely smoke if they are too cold. Changed stat - problem solved...not sure if that's your issue, but I would definitely look at operating temps when they are at idle.

  11. #11
    Join Date
    Nov 2009
    Location
    temecula, ca., usa
    Posts
    2,614

    Default Re: 6-71 TI Smoke At idle

    I don't think that is your particular problem but maverick44 makes a VERY good point about maintaining operating temp. A cold running engine starts having "health" issues in short order along with inordinate fuel consumption.

    Yes, you can do an "in frame" overhaul on a Detroit with the block in place because of the modular construction of the engine. That is, of course, if you have, or can gain, enough clearance under the block to access the rod caps. The rebuild is done with what are called "liner kits" where new cylinder liners with matched pistons are installed to, essentially, form a "new" cylinder in each hole. I would not recommend just throwing new rings at it because the new rings in a worn liner will have you right back where you are now in short order.

    As you can imagine, you are looking a very expensive repair in an overhaul like this. You had better really do your homework on selecting a mechanic/shop to help you with this or you can end up with some very pricey metal slag at the end of the exercise. There are several considerations and observations to be made at tear down to ensure that your engine block is worthy of being left in service as well. The liners come in several sizes to compensate for block wear but precise measurement must be done to fit them correctly to each hole. Because, each hole can be different from the next. Not a job for a weekend warrior or dock rat with a dock cart tool kit. Sadly, good 2 stroke Detroit techs were hard to find back when they still manufactured these engines and it has only gotten harder since.

    On the up side, these engines are some of the most reliable ever built. Not only that, but they are VERY rugged. It is my experience that, if you can live/deal with the cold start issue, you can probably still get a bunch of service out of this engine if you need to put off the repair and "save up".
    Last edited by jgmo; 03-25-2011 at 12:07 PM.

  12. #12

    Default Re: 6-71 TI Smoke At idle

    If you haven't made a decision yet, were in N.Y also and have extensive factory detriot expierence 1980. You may have a single cyl. problem, no big deal, but to tear it apart and only cure that is foolish there are very successful remedies that will work just fine on a 2 stroker that will make her pure again clean.

  13. #13

    Default Re: 6-71 TI Smoke At idle

    Hi,

    I notice you may be having or have had intercooler trouble, I work for a company called vestas aircoil who design and manufacture charge air coolers for large diesel engines. I will be happy to answer any questions you may have.

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