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2001 50 with 3406E RPM & GPH

Discussion in 'Post Yacht' started by B Dickinson, Jul 17, 2019.

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  1. B Dickinson, Jul 17, 2019
    #1
    B Dickinson

    B Dickinson New Member

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    Had our 50 pulled for a bunch of work to include dialing in props to rated WOT RPM of 2300. CAT survey showed 2240 +/- 20. Not very exact obviously. Anyway, asked Black Dog Props, who I have used for over 20 years to scan and rework wheels to give me another 50 RPM on each side. Back in water and not getting the extra 50 RPM - probably 2270 on port and 2285 on starboard. The curious thing is that now the port engine is showing a fuel burn of 2-3 more gallons per hour than the starboard. Prior to the wheel job they were both the exact same running the same RPM. Any ideas?
  2. Capt Ralph, Jul 17, 2019
    #2
    Capt Ralph

    Capt Ralph Senior Member

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    What boost numbers do you have? Color of exhaust? Fuel filter history?
    What fuel rates are they suppose to be consuming?
    When electronic pins are all open (WOT), the fine personality's of the engines just may show a lil difference.
    What fuel numbers do you get at cruise?
  3. B Dickinson, Jul 17, 2019
    #3
    B Dickinson

    B Dickinson New Member

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    Have to get boost numbers next time out. When I am running around 1850, 26 knots, both were showing 29-31 GPH (usually both steady @ 30) but both were the same. Now, same scenario, same RPM, same speed, port is showing 2-3 gph more than starboard. Only change is wheels. Fuel filters just changed and exhaust is clear (no white, blue or black) at all RPMs. Wheel specs, before and after - With finished specs almost identical don't know how it could be wheels...
    Port original pitch.... 33.079" cup.. .065"
    Stbd original pitch... 33.153" cup.. .060"
    Finished port pitch. 32.251" cup.. 065"
    Finished stbd pitch. 32.254" cup.. .065"
  4. Capt Ralph, Jul 17, 2019
    #4
    Capt Ralph

    Capt Ralph Senior Member

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    And your sure both clutches are the exact same?
    I'm leaning to air pressure.
  5. B Dickinson, Jul 17, 2019
    #5
    B Dickinson

    B Dickinson New Member

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    Clutches? You mean in gear or what?
  6. Capt Ralph, Jul 17, 2019
    #6
    Capt Ralph

    Capt Ralph Senior Member

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    I'm thinking more about this, Scratch this.


    Got another question; what is high idle or unloaded wot?
    Last edited: Jul 17, 2019
  7. B Dickinson, Jul 17, 2019
    #7
    B Dickinson

    B Dickinson New Member

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    Boat ran with both engines at exact same GPH before the wheel job.
  8. B Dickinson, Jul 17, 2019
    #8
    B Dickinson

    B Dickinson New Member

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    Will get this...
  9. B Dickinson, Jul 17, 2019
    #9
    B Dickinson

    B Dickinson New Member

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    Unloaded WOT port 2415, starboard 2370 with "throttle sensor calibration" code thrown
  10. Capt Ralph, Jul 17, 2019
    #10
    Capt Ralph

    Capt Ralph Senior Member

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    Well, there is some of your problems. If high idle is not a bit past 2400 on both, say near 2500 rpm, then loaded will not come close.
    Lets get a photo tach on those engines at high idle. You may be working with some slightly off tachs.
    This is easier than pulling a lap-top-tech out of bed.

    "throttle sensor calibration" Teleflex engine controls??
  11. Capt J, Jul 17, 2019
    #11
    Capt J

    Capt J Senior Member

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    I would've taken out more pitch and would've wanted to be closer to 2350 than 2300. They took out less than an inch. Usually it's an inch of pitch per 50 rpms.

    Anyways, if the boat is listing a little to port side, the port side will show higher load and more fuel burn. Could be that the port prop has a little more cup than stbd or something, but the scan numbers look really close. Next time you take the boat out, look at the load for both sides at cruise.
  12. Capt Ralph, Jul 17, 2019
    #12
    Capt Ralph

    Capt Ralph Senior Member

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    If the high idel is set low, you can take out miles of pitch and the RPM is not going to come up.
    Re-read OP and #9
    If you want 2400+ RPM, the pins have to get raised.
  13. Capt J, Jul 18, 2019
    #13
    Capt J

    Capt J Senior Member

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    He's looking for 2300 rpm's loaded. Motors are doing 1415 and 2370 with no load. I would verify the tachs are correct.
  14. Capt Ralph, Jul 18, 2019
    #14
    Capt Ralph

    Capt Ralph Senior Member

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    Yep, your correct, OP wanted 2300.
  15. Beau, Jul 19, 2019
    #15
    Beau

    Beau Senior Member

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    The props are pitched and cupped differently, isn't that going to effect fuel burn all things being the same?? The port seems to be working a little harder to make RPM, which effects fuel burn.
  16. Capt Ralph, Jul 19, 2019
    #16
    Capt Ralph

    Capt Ralph Senior Member

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    Finished port pitch. 32.251" cup.. 065"
    Finished stbd pitch. 32.254" cup.. .065"

    .003" is going to make a difference???
  17. Beau, Jul 19, 2019
    #17
    Beau

    Beau Senior Member

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    Dunno, but its different, and also changed from original? If nothing else is changed on the boat, wouldn't it be logical to suspect the propping change and difference?
  18. Capt Ralph, Jul 19, 2019
    #18
    Capt Ralph

    Capt Ralph Senior Member

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    Just a couple of new RPM. At the very top of the power band. I think the governor is pushing back or rite at it.
    Also a throttle position error.
    Electronic throttle and injectors.
    I'm hoping the OP is getting the tachs verified and the error looked into.
    And gets back with boost data on his next run.
  19. Capt J, Jul 19, 2019
    #19
    Capt J

    Capt J Senior Member

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    These 3406's calculated fuel burn off of a basic map based on ,RPM, injector pulse, and load. Chances are the old props might have been a little light on pitch on that side, or the boat was listing a little at cruise which will cause a few percent increase in load on the deeper side generally. 3 gph reading I would not worry about.
  20. Capt Ralph, Jul 19, 2019
    #20
    Capt Ralph

    Capt Ralph Senior Member

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    On the pins, I agree.
    The error concerns me.
    I still think we need to verify the tachs, fix the error and try again.

    I remember years ago fresh props doing strange things. Nobody mentioned they were dropped till they went back to the shop and the urine contest was launched. You just can not drop a big/heavy wheel and not expect some damage.

    I'm still looking for boost numbers after the error is corrected.
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