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Thread: Building a Super Mod 2 cylinder Mariner/Yamaha

  1. #1
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    Lightbulb Building a Super Mod 2 cylinder Mariner/Yamaha

    Because of the 70 CES Yamaha Thread several people are interested in building one of this power heads.

    The Motor

    In the states it was the Mariner 48, 55 and 60 hp, 2 cylinder, 15 inch, 1.84 or 1.71 gearcase, Yamaha made.
    In Mexico and Canada it was the Enduro or Yamaha brand.
    The motor was sold world wide as a commercial motor. Very sound and well build.
    You can still get new parts thru Canada and Mexico.

    Unlike the 70 hp Yamaha this motor has a solid steel crank, bolt on rods, twin carbs and a unique double exit exhaust system.

    You can get Boyensen reeds for them.
    You can use a 70 or 90 hp factory power trim on the long shaft version.
    You can use Pro 50 power trim on the short shaft version
    You can use the old in-line 4 and 6 cylinder Mercury power trim on either version

    Stock Performance

    We have only had one to try. It was a 55 hp Mariner long shaft. On a Delta and a VooDoo
    high 50's with NO MODS at all.

    What you should be able to get MOD

    80 to 90 hp

    Cylinder head MOD

    There are one or two people on this site that can make small chamber heads for these. Being a commercial motor, the head is not a performance head. A performance head will make a big difference.

    The Crank

    Unlike the OMC 45 cubic inch crank which weakens after being reworked, this crank does not. It can be stroked to perfect spec and blue printed.

    The Exhaust Chambers
    I am sure someone will come up with some performance ideas for them.

    Cost

    Lots of low cost stuff out there, good bang for the buck.

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    Default

    as i've a twin 40 mariner/yammy i'll be watching this thread with interest!

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    Default What is different about the exhaust tuner?


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    Default Yamaha parts.. are still avaliable

    http://www.boats.net/parts/search/Ya...ING/parts.html

    NOTE: YAMAHA DID NOT MAKE THE 15 inch model to my knowledge.

  5. #5
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    Default two cylinder outboard

    The 45ss 740cc twin easily will make 90hp on pump gas @ 7,000 rpm.
    The cranks are good right from SEAWAY Marine. all we did was check for T.I.R. on mains, Cryo by "Three Hundred Below" and go. Turned 8,200 never a bottom end failure. Never re-used 20yr old bottom end parts, not for another driver. looked at a lot of
    PWC twins to determine a canidate to reverse engineer. PWC engine builders will dyno all the way down to 3500 rpm which is a lot more meaningful than the other rec stuff out there.
    In order to make a intelligent response regarding your engine would need to know more about it.

    For the 45 did the following:

    1- mod head
    2- mod intake sys
    3- Behind sleeve porting
    4- mod water cooling
    5- adapt PWC Chamber from Kawasaki 750 ZXI or Yamaha Super Jet 701
    6- Light weight flex fly wheel
    Attached Images Attached Images    
    ANTHONY McCULLOCH
    modifiedoutboard@hotmail.com

    Some things never change!

    They Want it cheap..............

  6. #6
    FFX-61
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    they said "it hits like a piston port moda"

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

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    Lightbulb What I would try first

    The 2 cylinder motor is the same bore and stroke as the 90 Yamaha. We know that with a little porting, reeds and head mods to get in the 170 psi range. That motor is getting 20 to 25% more power [110 to 115 hp] easy.

    I would try the same in the 2 cylinder and go from there. Maybe try twin cow bell stainless exhaust tuners.

  8. #8
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    Maybe try twin cow bell stainless exhaust tuners.
    that would be the Ticket.

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

  9. #9
    modifiedoutboard OUTBOARDER's Avatar
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    Lightbulb

    Quote Originally Posted by Hounddog View Post
    The 2 cylinder motor is the same bore and stroke as the 90 Yamaha. We know that with a little porting, reeds and head mods to get in the 170 psi range. That motor is getting 20 to 25% more power [110 to 115 hp] easy.

    I would try the same in the 2 cylinder and go from there. Maybe try twin cow bell stainless exhaust tuners.
    Talked to OMC Tech that developed 45ss tuner and learned that they tried over a dozen pipes. Two cylinder will NEVER do what Triple does from a tuner cause there is no cross plugging going on. Two into one chamber is a 20+ hp bolt on , why guess??
    ANTHONY McCULLOCH
    modifiedoutboard@hotmail.com

    Some things never change!

    They Want it cheap..............

  10. #10
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    the exhaust on the 60DES was separate from each other, twin cow bell. held all 750cc records.at about 5500rpms about 40hp slams into the power band.

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

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