Tunnelstuff in Norway

Discussion in 'Outboard Forum' started by Joern Markset, Aug 19, 2017.

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  1. May 27, 2019 #121

    Joern Markset

    Joern Markset

    Joern Markset

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    Songe, Norway
    Had to test a new prototype of silencer for the Salisbury pipe, it made a big difference, but still a little loud.
     

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  2. May 27, 2019 #122

    GraysonTaylor

    GraysonTaylor

    GraysonTaylor

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    Is the gear drive an over drive or an under drive?
     
  3. May 27, 2019 #123

    Joern Markset

    Joern Markset

    Joern Markset

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    Underdrive, at the moment the pinion is 20Z and the spur is 29Z, ratio 1,45:1
     
  4. May 27, 2019 #124

    Julio Almazan

    Julio Almazan

    Julio Almazan

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    Thanks
     
  5. May 28, 2019 #125

    GraysonTaylor

    GraysonTaylor

    GraysonTaylor

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    That ratio takes 30k rpm down to just over 20k. I thought I once read that 20k was the best efficiency for a prop, but I can't remember where... keep us posted!
     
  6. May 28, 2019 #126

    Joern Markset

    Joern Markset

    Joern Markset

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    You are right, most props have very high slip percentage on high rpm. I experienced that when I was deep into eletric tunnels. for the Octura X series the slip increase drastically when you pass 30K rpm. Even from 25K the slip starts to increase.
    I`m now reading close to 38K rpm on the engine. Will shorten the header a little bit to see if I can reach maximum rpm around 42K.
    I have allready enough speed, and the acceleration is fantastic, so it will just be a bonus with some extra rpm`s.

    Also for the NR .46 I think gear will be a good solution, they work much better with a little less load and high rpm.
    Disadvantage is the extra weight you have to carry on the transom...
     
  7. Jun 9, 2019 #127

    Julio Almazan

    Julio Almazan

    Julio Almazan

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    Hi:
    I'm still trying to make a system similar to yours, thank you.
    If you have more pictures of your model, I am grateful to posted them here already.
    Some time ago, I had a car accident and I´m in rehab... When I´m better, I'll start building and posted here.
    Thanks for all.
     
  8. Jun 9, 2019 #128

    Joern Markset

    Joern Markset

    Joern Markset

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    Don`t think I have more pics than you can find in post #59 https://www.intlwaters.com/threads/tunnelstuff-in-norway.72995/page-3#post-712547
    It`s been quit some time since that boat was wet as there is new stuff and ideas coming up constantly...
    At the moment I`m putting my effort into gearboxes.
    Wish you a fast recovery.
     
  9. Jun 9, 2019 #129

    Christian Lucas

    Christian Lucas

    Christian Lucas

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    Hi,
    here in Europe the geard drive is very comon used. In FSR duration they run up to 90 size engine with gear. They use only a very small gear ratio of 1,2 - 1,3 : 1 , so the engine has a little moore punch out of the corner.
    The smaller engine go with higher gear ratio 2 : 1 and higher. Reason is to drive the bigger propeller dia that has less slip and better acceleration and pushing performance in and out of the corner, not for higher top speed.
    Very nice drive with the geared outborder setup.

    Happy Amps Christian
     
  10. Jun 10, 2019 #130

    Kris Flynn

    Kris Flynn

    Kris Flynn

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    Have you tried a small diameter carby? I have a KRE 10mm which is VERY quiet compared to the 11mm orlic.

    LMK if you want to try it? No proper testing to compare performance sorry
     

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