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Thread: Yamaha 4 stroke ?

  1. #1
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    Default Yamaha 4 stroke ?

    Can a 60 hp Yamaha 4 stroke be detuned to a 50 hp to run legal on the Kenai River?

  2. #2

    Default Same exact outboard

    Yamaha's fuel injected F50 and F60 are the same exact outboard, with the exception of the engine control unit (ECU = computer). And the only difference in that probably being a slightly more advanced fuel timing delivery.

    Same exact crank, pistons, valves, intake, fuel injection, etc., etc. - right down to every bolt and nut. They run the exact same compression, and the exact same rpm. You can compare each and every same-same part of the 50 and 60 right here:

    http://www.yamaha-motor.com/outboard/parts/home.aspx

    Part of the reason the same engine can have two different ratings is the tolerance in the hp rating system allowed by ICOMIA 28-83. Outboards are allowed to deviate +- 10% from their ratings. So if an outboard put out 55 hp, it could really be rated as either a 50 or a 60.

    If the 50 hp proposal is approved on the Kenai, it will be a simple piece of cake to run a 60, and virtually undetectable. The Yamaha 50 is already a 60. And having the largest displacement, most thrust, and all those features integrated into the tiller handle, it will be the engine of choice.

    Oh, almost forgot...If you've got an older carbureted 60 or 50, the differences are slightly more complex, like carburation calibrations, etc.

  3. #3
    Member aces-n-eights's Avatar
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    Default

    Quote Originally Posted by Big Water View Post
    Yamaha's fuel injected F50 and F60 are the same exact outboard, with the exception of the engine control unit (ECU = computer). And the only difference in that probably being a slightly more advanced fuel timing delivery.

    Same exact crank, pistons, valves, intake, fuel injection, etc., etc. - right down to every bolt and nut. They run the exact same compression, and the exact same rpm. You can compare each and every same-same part of the 50 and 60 right here...

    ...If the 50 hp proposal is approved on the Kenai...
    So could you buy a 50 and turn it into a 60 with an ECU swap?

    Also, the key word in your second thought is IF. The motor rules for the Kenai have not been changed YET, so it's still 35hp max, 2 stroke OK. The proposed legislation will allow up to 50 hp and only 4 stroke or direct fuel injection 2 strokes as of 1 Jan 08. Personally, my fear is the rules may change before they are signed into law so i'm not spending any money until i see the law. My $.02...

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    Default

    So I was about to type in a reply and my dear wife called me for dinner. I would have said much the same as aces n eights that the Kenai is still not 50 hp yet official and then called Deweys sometime back in regards to a 60 being easy to make into a 50 or versa visa and was told that only 40 hp could be made into 35 hp for the Kenai. I really think they misunderstood my question. So where can we find out the true answer if a 50-60 can go both ways and how to do it. The Kenai river cops will know the difference when they pull you over running a 60 on the Kenai -guaranteed!

  5. #5

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    So where can we find out the true answer if a 50-60 can go both ways and how to do it.
    Hopefully I've already given you that information.

    If you study the two outboards at the link I provided above, you will see that the only difference is the ECU. Every other part, bolt and nut, including the throttle cam, are exactly the same.

    The ECU on the 60 hp model is probably programmed with a slightly more advanced timing and fuel injection event. This would give it a few more hp. Add the fact that ICOMIA allows +-10% in the outboard manufacturer's ratings, and you can easily see how the same exact outboard can be both a 50 and a 60.

    Although the ECU can be easily changed out, it isn't going to be something that's easily detected. I believe the ECU is mounted behind the engine's intake and does not have a clearly visible part number. This is one reason the 50 hp proposal is unfortunate for the Kenai River....they might as well pass 60 hp.

  6. #6

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    Quote Originally Posted by Big Water View Post
    This is one reason the 50 hp proposal is unfortunate for the Kenai River....they might as well pass 60 hp.
    This assumes that many people will know how to change out an ECU and try to cheat the system. I'm dubious that a reputable dealer like Dewey's would do this for you. I'm in the market for a new boat next year and i'm pretty sure I won't want to void my warranty by doing such a change myself.

    Thanks for sharing the comparison of the 50 and 60, Big Water. I suspected they were the same.

  7. #7
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    Default

    You'd have to swap out the cowling as well, so it won't say "60" on it ...and you better make darn sure the changes were documented and provable.

    BTW, 50 hp becomes legal on the Kenai in '08. Check the rules and don't jump the gun..

    bd

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    Member aces-n-eights's Avatar
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    Default

    Quote Originally Posted by tananaBrian View Post

    BTW, 50 hp becomes legal on the Kenai in '08. Check the rules and don't jump the gun..

    bd
    I don't think that's right. The PROPOSED rules will allow 50 hp and only 4 stroke or 2 stroke DFI engines, but that has not been signed into law. Does anyone know the process and timeline for this to be signed into law?

  9. #9

    Default process, what process

    Quote Originally Posted by aces-n-eights View Post
    I don't think that's right. The PROPOSED rules will allow 50 hp and only 4 stroke or 2 stroke DFI engines, but that has not been signed into law. Does anyone know the process and timeline for this to be signed into law?
    Deadmans is right, this is still a proposed change - Word from the Atwood tower is that they put the regs on hold for awhile, asked a few more questions and are now back to putting the finishing touches on the regs as previously written. It not a law until its approved by dept of law and the ADNR commissioner.

    I'd hardly call this whole episode in regulation making a "process"
    --

    Whomever at deweys told you that you can't detune a 50 to 35 shouldn't be answering the phone. Most of the dedicated Kenai boats are running this configuration.

    There are lots of ways to beat the HP regulations, a part number, one wrench, a screwdriver and a pair of pliers - to avoid getting caught, you only have to show restraint on the top end. 60 HP is out there now.

  10. #10

    Default

    You'd have to swap out the cowling as well, so it won't say "60" on it
    Actually it's just a decal. The cowlings are exactly the same.

    There is a metal ID tag on the bracket, but it would be easy to switch that too.


    60 HP is out there now.
    Yep. If the 50hp increase goes through, the 60's will be harder to catch.

  11. #11

    Default One more bit of info

    The 50HP-on-the-Kenai Regs need to be out by the 19th of this month. Otherwise the "process" starts over - it'll be a year since the proposal was published, and that is a deadline for action. Its gonna happen, unless something dramatic happens in the next week.

    Re the detuning of 60HP, I'd call to find out about this; if it is a decision that influences your $6k purchase. You can call ADNR's Jack Sinclair @ 262-5581 xtn 1. There was a rumor that the SN on the motor must indicate 50HP. In which you'd want to purchase a 50HP motor and an extra 60 HP, ECU ~ $600, so you can "tune-up" your motor - you won't be alone!!.

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