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Thread: By Passing the Rev-limiter

  1. #21
    pdt
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    how is the hp calculated if the torque has fallen off by 1,600 rpms ?
    this is a huge gap away from the max powercurve !!!!!

    ive never ever come across an engine that develops its highest power at its highest rpms before, not even on race bikes and race cars.

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    Quote Originally Posted by pdt View Post
    how is the hp calculated if the torque has fallen off by 1,600 rpms ?
    this is a huge gap away from the max powercurve !!!!!

    ive never ever come across an engine that develops its highest power at its highest rpms before, not even on race bikes and race cars.
    Hey, phillnjack, do some research on the internet. There's plenty already out there instead of challenging what's been said here.

  3. #23
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    hp is a calculation from torque and rpm so clearly hp can climb when torque goes down

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    Rev limiters are installed by the factory to keep the engine at the rpm they feel is reasonable for the multiple uses intended without over rev for warranty claimes for a damaged engine. These outboards can run quite well above the rpm the factory limits them to as hp increases above max torque to a point then drops off, but the owner would be out of warranty if the limiter is disabled, but in Emustard'd case his 1992 warranty is way gone, he should so go for more revs and more pitch if the engine power is there.

    As an example with my race 1972 Merc 25ss 2 cylindere Mercury (no rev limiter) states in the specs max recommended rpm = 6600. Well that didn't win races so all us 25ss guys raised them up increased the prop pitch and ran these engines at 7100+ with more oil than the recommended 25:1 and much greater speeds.
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    Quote Originally Posted by zul8tr View Post
    Rev limiters are installed by the factory to keep the engine at the rpm they feel is reasonable for the multiple uses intended without over rev for warranty claimes for a damaged engine. These outboards can run quite well above the rpm the factory limits them to as hp increases above max torque to a point then drops off, but the owner would be out of warranty if the limiter is disabled, but in Emustard'd case his 1992 warranty is way gone, he should so go for more revs and more pitch if the engine power is there.

    As an example with my race 1972 Merc 25ss 2 cylindere Mercury (no rev limiter) states in the specs max recommended rpm = 6600. Well that didn't win races so all us 25ss guys raised them up increased the prop pitch and ran these engines at 7100+ with more oil than the recommended 25:1 and much greater speeds.
    That works on light boat where you decrease the drag so dont need the torque and the engine will either have a same hp or more as the rpm goes higher

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    Quote Originally Posted by Emustard View Post
    Hey just wanted to know if any one can help answer this question, can I by pass my rev-limiter in my 1990 20hp evinrude?

    Rev-limiter cuts in at 6100 rpms can I can't I wire or disconnect something?
    there is a service bulletin showing where to drill a hole in the pack to disconnect the rev limiter if it has one
    or just use an earlier pack as they didnt have limiters

  7. #27
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    Hey thanks for the tip, I ended up buying a no-rev limiter from CDI. installed it this weekend and it worked great hopefully some more runs this weekend. Thanks everyone for your help.

  8. #28
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    you can drill it, but if you miss, always used the non rev limiter box my self. stock 75hp omc 49cubes, hp and torque peak together at about 5800rpms, after that torque starts to fade or fall off, hp however holds at 75hp all the way to 7800rpms then hp starts to fade, stock, out the box, gots to go fix boats........

    Part one of "Secrets of the OMC Mod 50" : http://www.boatracingfacts.com/forums/showthread.php?t=2052

  9. #29
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    55hp omc head is not a good choice, someone asked

    Part one of "Secrets of the OMC Mod 50" : http://www.boatracingfacts.com/forums/showthread.php?t=2052

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    Quote Originally Posted by Fast Fred View Post
    you can drill it, but if you miss, always used the non rev limiter box my self. stock 75hp omc 49cubes, hp and torque peak together at about 5800rpms, after that torque starts to fade or fall off, hp however holds at 75hp all the way to 7800rpms then hp starts to fade, stock, out the box, gots to go fix boats........
    no argument there Fred
    I am surprised the 75 makes power to 7800, so light boats prop'd over 7500?

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