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Thread: 2 Stroke engines and CC rating, why is Merc 50 3cyl so much more than Yammy?

  1. #1

    2 Stroke engines and CC rating, why is Merc 50 3cyl so much more than Yammy?

    Im a huge yamaha fan, have always considered them the premier engine, outside 4 strokes, where now imo they are also they strongest built of the 4s, but Honda with its pedigree being entirely in 4s being the outright most economical on fuel.

    Anyway, I digress.

    I noticed the Mercury 2stroke 50hp 3Cyl is rated at 967cc piston displacement.

    Where the Yamaha (and tohatsu) are only around 700cc piston displacement.

    What gives there, surely that gives the Mercury a huge advantage in torque/hole shot?

    I am not an engineer in marine mechanics, but this just seems wrong some how, what is the real world difference in 267cc difference? I know with motorcycles it is significant.

  2. #2

    Re: 2 Stroke engines and CC rating, why is Merc 50 3cyl so much more than Yammy?

    I had a 50hp mariner (mercury) 3cyl on a 15ft boat it had plenty of power and the hull was rated to 75hp!!

  3. #3

    Re: 2 Stroke engines and CC rating, why is Merc 50 3cyl so much more than Yammy?

    The reason is simple.

    All manufacturers share blocks between multiple models - eg the block on a 50hp might also be the same one used for the 60 hp and maybe even the 70. They just tweak/tune/add features to create 2 or 3 different hp engines from the same basic block.

    So at 50 hp, the Merc might be the baby of the range that uses the 967cc block. The downside will likely be that its also the heaviest in that hp.

    And the Yammy might be the top end of the 700cc block range. And probably will be fair bit lighter than the Merc in the same hp.
    Note to self: Don't argue with an idiot. They will only bring you down to their level and beat you with experience....

  4. #4

    Re: 2 Stroke engines and CC rating, why is Merc 50 3cyl so much more than Yammy?

    But does having extra CC give you a real world torque difference?

  5. #5
    Ausfish Addict disorderly's Avatar
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    Re: 2 Stroke engines and CC rating, why is Merc 50 3cyl so much more than Yammy?

    A wise man once said "There's no replacement for displacement" ..

  6. #6

    Re: 2 Stroke engines and CC rating, why is Merc 50 3cyl so much more than Yammy?

    And that "wise man" is getting pretty old now, modern technology has way over taken the old "just make it bigger" mantra.

  7. #7
    Ausfish Addict disorderly's Avatar
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    Re: 2 Stroke engines and CC rating, why is Merc 50 3cyl so much more than Yammy?

    I would hardly be calling those old 2 stroke motors "modern technology' Noel...

  8. #8

    Re: 2 Stroke engines and CC rating, why is Merc 50 3cyl so much more than Yammy?

    Quote Originally Posted by GlobbyGuts View Post
    But does having extra CC give you a real world torque difference?
    Yeah its noticable in small outboards once u start running bigger engines prop pitch and diameters come into play with boat sizes boat weights different planning hulls etc.. kinda like a multi combination

    With little horse power most people are just bunging it on a tinny

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