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Thread: yamaha oil mix

  1. #1
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    Default yamaha oil mix

    i have a old yamaha 25 outboard, does anyone happen to know the correct oil mix ratio.
    thanks in anticipation

  2. #2
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    Default Re: yamaha oil mix

    Depends how old could be 50/1 or 100/1

  3. #3
    Gordonmc's Avatar
    Gordonmc is offline Registered User
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    Default Re: yamaha oil mix

    Safest to run on 50/1.
    My Mercury book said 100/1 but received wisdom is that 50/1 will prolong an old motor's life. It doesn't smoke and starts on the second pull - always.
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  4. #4
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    Default Re: yamaha oil mix

    NO NO NO - must use correct mix.

    not enough oil = engine wears out
    too much oil = less petrol = engine runs weak = hot = burns plug & piston

    If your yam has been made in the last 20 years, then 100/1 sounds correct, but check

    Mind you, if you only make short trips (˝ mile) then it probably dont matter. The thing will die of corrosion first as have my last 2 yams (2hp both 100/1)

    Grat engines. one thing though, at the end of the season, run it in your raiwater barrel to get rid of the salt, and use any left over fuel for making molotov cocktails, cos of evaporation of the lighter fractions, it will have become very "rich" and sooty burning by spring.
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  5. #5
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    Default Re: yamaha oil mix

    NO NO NO - must use correct mix.

    not enough oil = engine wears out
    too much oil = less petrol = engine runs weak = hot = burns plug & piston

    If your yam has been made in the last 20 years, then 100/1 sounds correct, but check

    Mind you, if you only make short trips (˝ mile) then it probably dont matter. The thing will die of corrosion first as have my last 2 yams (2hp both 100/1)

    Great engines. one thing though, at the end of the season, run it in your raiwater barrel to get rid of the salt, and use any left over fuel for making molotov cocktails, cos of evaporation of the lighter fractions, it will have become very "rich" and sooty burning by spring.
    Ad littora tendit

  6. #6
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    Default Re: yamaha oil mix

    ugh - seeing double - msh be somethin i drunk
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  7. #7
    LORDNELSON is offline Registered User
    Location : West Sussex, England
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    Default Re: yamaha oil mix

    I seem to remember that for my 2HP Yamaha the book (which is on my boat and so I cannot refer to it) says 1:100 for pleasure users and 1:50 for commercial users. For the last 7 years I have used mine for pleasure with 1:50 mix and it is still going strong! When I have dissembled it to clear the salt out of cooling passages there is a very satisfactory amount of oil evident around the piston.

  8. #8
    jerryat is offline Registered User
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    Default Re: yamaha oil mix

    Yes, I agree. I was VERY strongly advised by the engineer from whom I bought my Mariner to use 50:1 not the 'recommended' 100:1. He was adamannt that the engine would last considerably longer. I sold that one after 17 years and it was still going strong.

    I run my current Yam on 50:1 also, so hope that'll last at least as long.

    Cheers Jerry

  9. #9
    Join Date
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    Default Re: yamaha oil mix

    Let me think this one through.....

    100:1 = 100drops of petrol and 1 drop of oil
    50:1 = 100 drops of petrol and 2 drops of oil
    richer oil mix = leaner petrol mix (O.K.) = over heating and burning of the piston - NO way on earth will that happen by running on 50:1 instead of 100:1 - Stop scaremongering.
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  10. #10
    Join Date
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    Default Re: yamaha oil mix

    wanna bet on how many people can measure that accurately anyway?

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