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  1. #1

    Default 12V71TI Rpms not stable above 1850.

    Hi,

    After my recent rebuild on both port and starboard engines, 12V71TIs 850hp, I noticed that I can not maintain a steady RPM above 1825-1850. The moment I move my throttle to 1850 on either the port or the starboard, the engine RPM runs to 2200-2250. My WOT is 2350-2375. This happens to each engine only under load. It also happens when using the old school Glendenning synchronizer. Also notice when using synchro that RPM of Master Engine some time goes from 1825 to 1875 and back down again. This make maintaining a straight course difficult. At RPMs lower that 1800 everything is fine and steady.

    The Fuel Modulators are currently disconnected.

    Thanks,
    Ozzy

  2. #2
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    Default Re: 12V71TI Rpms not stable above 1850.

    If the engines start easily and idle smoothly, there is likely nothing wrong with your tunes. It certainly sounds like a throttle actuator problem but I'm not familiar with the Glendenning system.
    It sounds like a cable is binding, giving you a false throttle setting and then "unsticking" and moving the throttles to where they would have been if not for the sticking.

    Having someone work the throttles while someone else looks for the bad spot is all I can suggest from here.

    This does not sound like a governor problem. Hopefully, someone here has better advice and experience with that system to share.

    Good luck.

  3. #3

    Default Re: 12V71TI Rpms not stable above 1850.

    Ok.. thanks. Yes we have looked at the throttle cable and it doesnt seem to be sticking. Both engines are showing this problem.
    How about the adjustment of the Spring throttle tension'er? How does that get adjusted?

  4. #4
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    Default Re: 12V71TI Rpms not stable above 1850.

    Well, we may run in to some more nomenclature discrepancies here. Pictures can help clarify things sometimes. I don't know everything and I don't know what a "Spring throttle tensioner" is.
    There is something called a booter spring that is used to "soften" the throttle feel. It is a 3/4" X 5 1/2" coil spring that attaches to the throttle lever at one end and a 2 to 3" long eye bolt at the other. The eye bolt is attached to a stand-off bracket on the blower housing and is used to adjust the booster spring.

    Could that be what we're talking about?

    I've been looking at the Glendenning controller and the first thing I notice is that the idle setting of the slave engine needs to be adjusted LOWER than the idle set of the lead. Also, tha Max.No Load of the slave is set HIGHER than the lead.
    Are your engines srt up this way?

    Have you prrformed the Glendenning "governor lever tension test"? I do see that the booster spring is involved and it looks as if this may be your issue.

    If you don't have the documentation, I can walk you through it.
    Last edited by jgmo; 05-16-2017 at 07:29 PM.

  5. #5

    Default Re: 12V71TI Rpms not stable above 1850.

    The problem happens with or without the Glendenning sychro on, When the Sychro is on and the Master engine runs away the slave follows. When the slave runs away the Glendenning bring it back.

    Yes, please walk me through just is case its that.

    Thanks!

  6. #6
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    Default Re: 12V71TI Rpms not stable above 1850.

    First, you MUST make sure that your slave rpms at idle are lower than your lead idle rpms and that the slave MAX. NO LOAD rpms are HIGHER than your lead MAX. NO LOAD rpms.
    The throttle's control goes THROUGH the synchro whether it's on or off.

    Adjust booster spring:
    Engine off, move speed lever of governor to idle position. Loosen the spring retaining nut on the lever as well as the lock nuts on the eyebolt at the other end of the spring.

    Move the spring retaining bolt in the slot on the lever until it is on center or slightly over center toward idle position through an imaginary line through the bolt, lever shaft and eyebolt. Hold it there and tighten the retaining nut.

    Start the engine and move the throttle lever to MAX. NO LOAD position and quickly release it. The throttle lever should return to idle. If it doesn't, loosen the spring tension.

    If it DOES return to idle, start increasing the spring tension until it doesn't return to idle and then back it off until it does again.

    As you can see, you're looking for a "sweet spot" of tension on the spring that will return the lever to idle.....but just barely.

    I don't care for springs because they change tension constantly. But they are still a big part of our mechanical lives.

    Good luck.
    Last edited by jgmo; 05-19-2017 at 05:40 PM.

  7. #7

    Default Re: 12V71TI Rpms not stable above 1850.

    Thanks for the great info.

    Do you have link showing some pics of the parts you are describing?

    I can tell you what I know at the moment. Master Engine idle RPM are lower that Slave. Not sure about MAX no load rims, I have to check. Also the Master engine works a lot more than the slave. Before the rebuilds the Master was more worn out and Always steams a lot more than the slave.

    Could this be related to idle calibration?

    Ozzy

  8. #8
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    Thumbs up Re: 12V71TI Rpms not stable above 1850.

    There's lots of stuff about the synchronizer online. The link below has the engine speed info I gave you and a test you can do for the booster spring tension. However, I would contact Glendenning and see if they could help you source one of their manuals for your specific synchronizer and have it on the boat at all times.

    https://www.google.com/url?sa=t&sour...TiRAziEUyxVj1Q

    Other than that, I'm simply referencing my 1993 Detroit Diesel V 71 service manual. Another form of documentation I would strongly urge you to have on the boat at all times.

    There are probably later editions available that may also have the injector info you were asking about on another post.

    Good luck Captain.

    P.S.
    I just checked the link above and it doesn't take you to the page I intended. I'm sorry, but I can't figure out how to send it the way I want. I got to the pertinent page by clicking on a header that said:
    "Glendenning synchronizer parts"
    Last edited by jgmo; 05-24-2017 at 01:23 PM.

  9. #9

    Default Re: 12V71TI Rpms not stable above 1850.

    Ok. thanks..

    I have an older V71 manual. What section is it in? It might have pictures.

    Thanks for all your help!

  10. #10
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    Default Re: 12V71TI Rpms not stable above 1850.

    The booster spring info is in tune up, section 14. There's a pretty good picture of it illustrating the adjustment. But, you need to follow the Glendenning guide for adjustment. The procedure in the engine manual is for a single throttle only. The adjustment is pretty much identical but the assessment procedure for identifying the need for adjustment is slightly different with a synchronizer set up.

    And, of course, you have to first adjust the two idle and two MAX. NO LOAD speeds to match the Glendenning prerequisites.

    From what you say, your engine speed settings, as they relate to one another and to the synchronizer requirements, are incorrect.

    Good luck.

  11. #11

    Default Re: 12V71TI Rpms not stable above 1850.

    Jgmo,

    The glendenning diagram has the port as the slave .

    My port is the Master. Does that mean the rpm numbers u gave me should be reversed?

    Then I just need to adjust the spring.

    thanks

  12. #12
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    Default Re: 12V71TI Rpms not stable above 1850.

    Port, stbd, right, left......it doesn't matter. Whomever installed your synchro chose the port as the master due to distance from wheelhouse, cable routing, convenience or, possibly, all three. The Glendenning manual speaks to this. It matters not which side was selected as master, the master would still have higher rpm at idle and lower rpm at MAX. NO LOAD than the slave.

  13. #13

    Default Re: 12V71TI Rpms not stable above 1850.

    How much difference at idle and at MAX. No load?

  14. #14
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    Default Re: 12V71TI Rpms not stable above 1850.

    These engines have a minimum idle requirement of 500 rpm. Most of us set idle at 550 or 600. On some vessels the skipper will have it set a bit higher to gain better steering control with the throttle fully closed.

    Not knowing what idle you prefer, I am simply going to say leave your port (master) where it is if it's at 550 or higher and try to adjust stbd. (slave) 25 rpm LOWER.

    You say your MAX. now is 2350 to 2375.
    I would suggest that you re-adjust your port (master) to 2300 and your stbd. (slave) to 2350.

    These are just suggestions and you should "tweak" them to what you feel is conducive to what gives you the best "feel" at your helm.

  15. #15

    Default Re: 12V71TI Rpms not stable above 1850.

    bypass the glenn.then retry [email protected]

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