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Thread: Fast Fred's Secrets of the OMC MOD50's Thread #1

  1. #131
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    Default Mod 50

    We tested just about every carb combination you could think of at the time. It was possible to see a few more horsepower with a larger carb but when tested on the race course lap times would always suffer. Just not enough signal per cylinder to make the larger carb work well. We did find that "buzz bottles", like those used on snowmobiles helped acceleration.

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    Team Member JohnsonM50's Avatar
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    Quote Originally Posted by Mark75H
    Exactly correct.

    Reed stop is a misnomer, they stop harmonic vibration of the reed, not limit opening distance (on most motors). On a few motors Mercury lowered the stop height to reduce the power in a second tier motor (115 vs 135, etc), but I do not know of any other motors where the maker set them lower causing a power decrease. Generally reed stops are there to increase reed life, no other reason. If you want the reeds to break, by all means, remove the "stops"

    Boysen "Dual Stage" type reeds are their own vibration dampeners and probably don't need stops on most motors
    Thanks,, um I mean no thanks. My choice of motor havin petal reeds smaller at the base, harmonic vibes would probably involve twisting, [even a back yarder like me knows how much faster that would break em.] Im just tryin to learn from the wealth of knowledge that is you guys.

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    Sam Cullis Mark75H's Avatar
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    Jim, you got me thinking about the M31 block again ... putting the exhaust on the other side took advantage of the reversed firing order, but if that was the main advantage you could have just run the original block backwards. Now I'm thinking the exhaust on the other side was just one of several things that were different. Did the M31 block give more room for a bigger exhaust chamber under the same cowl, too?
    Since 1925, about 150 different racing outboards have been made.


  4. #134
    David_L6
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    Quote Originally Posted by NERSTROM
    We did find that "buzz bottles", like those used on snowmobiles helped acceleration.
    What is a "buzz bottle"?
    (I live in Louisiana. We've heard of snow and snowmobiles........)

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    Default Mod 50- M31

    The exhaust was put on the other side to take advantage of the piston thrusting against that side on the downstroke for a better seal. This does not change the tuning effect due to firing order, still the same 1-2-3. When testing V6's we had noted that one bank always made more power than the other.

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    What is a "buzz bottle"?
    i think it's a chamber on the side of the intake, not sure if it 's before or after
    the reed block, seen one on a Yamaha, looked like a oil jug stickin out the side of the ruba intake.

    take advantage of the piston thrusting against that side on the downstroke for a better seal.
    some one told me that was why that was done, for the seal.

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    ok, talk about some cranks for this power,
    hears the two to choose from


    got to run for now, but i'll get back and talk about the dif' between the two

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    ok, hears what i know about the two, (top pic) the one on tne right is cast,
    made from a molten mix , pored in to a sand mold, lite machineing, hard cromed,
    it's give away mark is the hollow throughs, and the finish of the counters.
    light weight, reg- med duty.
    on the left is Forged, a piece of stock is heated cherry glowin red, it is tranfured
    to a press ware it is pressed with a bunch of tons of psi, until it is condenced
    in to a smaller workable shape, machined off , hard cromed.
    give away marks, hevy machine work on counters, no hollow throughs.
    heaver than cast, as bullet proof as it gets

  9. #139
    David_L6
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    Is the forged crank really necessary?

    I don't know what the Formula E / Super E guys are running, but I don't remember ever hearing of broken cranks. See sheared Woodruff keys once in a while though.

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    Default Balance

    One has better balance than the other. Still not good by any stretch of the term. The dam things still will vibrate like crazy. OMC tolerences are rather generous.

    I think Ralph sheared the key in his engine at Centrallia on Sunday. We could not get it started for SER. Looked and the timing was way off, and it bit the crap out of us while trying to crank it.

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