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MTU series 2000 M94 Secondary turbos coming in and out?

Discussion in 'Engines' started by Cawley, Dec 17, 2019.

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  1. Cawley, Dec 17, 2019
    #1
    Cawley

    Cawley New Member

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    M94 2000 series 10 cylinder. Boat 2012 Sunseeker with 700hrs. Problem started out of no where. Upon acceleration as soon as she hits 1850rpm the secondary turbos come in and out about 4-6 times then levels out and runs fine. Happens with both engines. Does it with sync on or off... Have had numerous professionals look at them with the computer hooked up. None of them can figure it out. We have done 6 sea trials. Bottom paint is fresh. Props were checked and fine. All filters are new and clean. Full service was done... With the engines on the computer, all parameters are fine according to MTU reps. ZF controls were checked and are working properly. They are the original props that were tested by MTU and Sunseeker during initial sea trials. Sunseeker says these are the props it should run. I have been running the boat for 2 years. Problem started 6 months ago. Nobody can figure out whats going on. Any help would be great. My boss is tired of spending money to get no real answers. It is also beginning to make me look bad..... Please help! Thanks in advance.
  2. olderboater, Dec 17, 2019
    #2
    olderboater

    olderboater Senior Member

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    What RPM are you getting at WOT?
  3. Cawley, Dec 17, 2019
    #3
    Cawley

    Cawley New Member

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    Just under 2400. About 2370 on the port and 2390 on the star. I am told this ok even though the max is 2450
  4. Capt Ralph, Dec 17, 2019
    #4
    Capt Ralph

    Capt Ralph Senior Member

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    Waist gate slow or sticking. Common issue with dock queens.
    Seems to be becoming an issue with dual turbo setups with waist gates.
    Next issue of course would be air pressure after the A/C or the A/P sensor there.

    New boat to you? Or new symptom?
    Last time it ran correctly? Any work or service since or rite before this new symptom?
    If your not making RPM correctly, all bets of correct operation is off....
  5. olderboater, Dec 17, 2019
    #5
    olderboater

    olderboater Senior Member

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    If that was with a light load then I'd be concerned about the props. Sunseeker telling you the right props are on it is not enough by any means. I've seen cases where they definitely weren't right and weren't even the pitch they were marked as. I'm never happy with not reaching Max RPM at light load.
  6. Cawley, Dec 17, 2019
    #6
    Cawley

    Cawley New Member

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    I have been on the boat 2 years. Problem started out of no where 6 mos ago. Thanks for the help
  7. Cawley, Dec 17, 2019
    #7
    Cawley

    Cawley New Member

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    I agree... However I have run the boat much heavier than it is now. IE dingy, full fuel, etc for two years. Never had a problem. Now boat is light IE dingy kept on dock. Fuel is below half. Bottom paint is fresh. Problem out of no where from one day to the next...
  8. Capt Ralph, Dec 17, 2019
    #8
    Capt Ralph

    Capt Ralph Senior Member

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    Last fuel filter changes?
    What shop is looking at it?

    Max no load rpm? If max high idle good, lets plan on fixing those props soon.
  9. Cawley, Dec 17, 2019
    #9
    Cawley

    Cawley New Member

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    Thanks for the fast response. Filters are new, Boat had a full service while in the yard for bottom job. Also props were sent out while at the yard. Problem was there before and after yard visit. I am told by my tech to not rev the engines past 1,500 without a load. He says it messes with valves in the trannies so I have not done it. Certified MTU shop looking at it. 6 sea trials with computer hooked up. No answers yet. Changed secondary turbo shift points, no change. Turbo housing rebuild, no difference. ZF controls checked, no difference. Puzzling...
  10. Capt J, Dec 17, 2019
    #10
    Capt J

    Capt J Senior Member

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    I ran a set of 12v2000s that did the exact same thing. Not sure what caused it or what, but once boat got to 1850, it fell on it's face, then secondary turbo's kicked in and it accelerated like a rocket. Seems like the boat is overpropped, Sunseekers like to be on the underpropped side of things and spinning the props faster at 80% load. I am running a new Manhattan and fuel fuel/water boat was 80-100 rpms overpropped…….cruise speed was slow, we never saw more than 24.5 knots at 80% when getting light on fuel, took 2" of pitch out, not boat starts out at 25+ knots full/fuel water.....and burn off a little and we're cruising at 27-27.5 knots. Being overpropped is probably part of the turbo lag, but not all of the problem. Did this occur after the boat was up North and then came down to Florida where the air temp and water temp is warmer? My guess, the aftercoolers are getting dirty. Take a hard look at your EGT data and boost pressure from your seatrials and compare to factory spec.
  11. Capt Ralph, Dec 17, 2019
    #11
    Capt Ralph

    Capt Ralph Senior Member

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    Never heard of that in a ZF clutch. I'm open to learn.
    So how do you validate high idle?
    Try this again..??
    Were all family here. Lack of text here I assume someone your not proud of.

    Last pray for information,, Any % load data??
    What load does the symptom occur?

    Any data on fuel pressures also?
    Last edited: Dec 17, 2019
  12. mapism, Dec 18, 2019
    #12
    mapism

    mapism Senior Member

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    Positively +1.
    Unless the chap who said that also specified another way to check high idle (which I very much doubt that exists), just suggesting to never exceed 1500 unloaded sounds like a total nonsense.

    Back to the point, the problem is not unheard of, with series 2000 engines.
    I know of a chap who was suggested from his MTU dealer to just get used to live with the problem, i.e. cruising at either 50 rpm above or below the critical point - which as I recall is around 1850 also with his boat.
    Btw, also for him, the problem only appeared after a few years, though in his case it began just occasionally, and then more frequently, eventually becoming a regular pattern.

    PS: Which S/skr, Manhattan 73, possibly?
    Anyhow, I agree with olderboater. With clean hull & props, good filters etc., I would have the props tuned by a good prop shop, in order to reach the rated WOT, regardless of the twin turbos issue.
    Last edited: Dec 18, 2019
  13. Cawley, Dec 18, 2019
    #13
    Cawley

    Cawley New Member

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    Thank you guys for all the responses.... This site is a wealth of info... Yes it is a 73 Manhattan... Sounds like we need to play with the props. It is just weird that it happened out of nowhere with a light load...
  14. Capt Ralph, Dec 18, 2019
    #14
    Capt Ralph

    Capt Ralph Senior Member

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    Does heavy - light ship weight load result in same WOT rpm?
    What % engine loads are reported?
  15. Cawley, Dec 18, 2019
    #15
    Cawley

    Cawley New Member

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    Yes the WOT rpm does change a little according to weight. Full of fuel and water. I see around 2340+-. Light I see just under 2400. I can't remember the exact load percentage, I would have to look at the data again. But we cruise the boat around 1900-2000 rpm. Seems to be around 80%. 24 knots. We have another sea trial scheduled after the new year. I will revisit all this with the techs. Thanks again....
  16. Capt Ralph, Dec 18, 2019
    #16
    Capt Ralph

    Capt Ralph Senior Member

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    Were all learning more as we go.
    Please keep a log of engine data and share it with us after your next trial.

    Safe and Merry Christmas & New Year to all.
  17. olderboater, Dec 18, 2019
    #17
    olderboater

    olderboater Senior Member

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    It takes very little to change the performance of props. A little wear, a little sand, a little shift, things that happen that you're not even aware of. This is why you hear of those with high performance boats constantly "tuning" their props.
  18. mapism, Dec 18, 2019
    #18
    mapism

    mapism Senior Member

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    Not an outrageous difference, and in this sense I can see why someone told you it's acceptable.
    But if she were my boat, I'd definitely ask a good prop shop to re-pitch, aiming for 100 rpm more.
    Which means reaching the rated WOT speed on full load - i.e. the ideal condition, imho.
    Of course, I'm assuming that your numbers were achieved with everything else in good shape - clean hull, etc.

    On top of rpm and speed, remember to specify to the prop shop also the gear ratio, which is important for them, to calculate the slip.
    I don't think they should care about engines load, since the assumption is 100% at WOT anyway.
    The number is just relevant for your cruise speed optimization, and in this sense it's a very good idea to keep track of the "before" numbers, to compare them with the "after".
  19. olderboater, Dec 18, 2019
    #19
    olderboater

    olderboater Senior Member

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    With no load or an extremely light load, we expect to exceed rated RPM by 25 to 50, as, in normal running, you'll never have no load or that exceptionally light load.
  20. Capt J, Dec 18, 2019
    #20
    Capt J

    Capt J Senior Member

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    Fully loaded with fuel and water I like to see 50 rpms over WOT. On trips you'll have people, luggage, food and drinks, etc. I'd like to see 100 rpms more which should equal to taking out about 2" pitch. The boat will also pick up speed at cruise and ride better (more stern lift) if you run it 80% versus 80%
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