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    Gas oil ratio

    I’ve just got a 79 55hp Johnson. What’s a good oil gas mix ratio to use? Previous owner said he thinks it was 50:1 kinda seems high but I know no different

    #2
    If memory serves me right, that's what our old Johnsons used to run growing up. But, my memory doesn't always serve me right...
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    -My computer, my time, my opinions

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      #3
      http://www.marineengine.com/boat-for...Johnson-motors

      -----------------------------------------
      -My computer, my time, my opinions

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        #4
        Great web site lots of help,
        https://forums.iboats.com
        Don

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          #5
          50:1 for my old Chrsyler .
          But my newer chainsaw calls out 32:1 .
          weed eater is 40:1
          Why are they all different ?

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            #6
            50 to 1 is good. If you get a little too much oil in that won't hurt. Try not to get too little in. Also use NO ethanol. Just regular unleaded. It will save you many hours of mechanical maintenance. Also before making a serious trip, change the water pump impellor. If the motor sat for some time it will be suspect.

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              #7
              Yup 50:1 for that Johnson. ...1 pint per six gallons. If it ain't smokn' it ain't running.... Johnson's are known for that....maybe that is why they were such good engines.

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                #8
                Originally posted by rjd View Post
                50:1 for my old Chrsyler .
                But my newer chainsaw calls out 32:1 .
                weed eater is 40:1
                Why are they all different ?
                One reason that they're different is that your chainsaw and weed eater are both air-cooled, while the outboard is water-cooled. It's likely that the smaller, air-cooled engines run at a higher temperature than the outboard, and that the air cooled engines have a wider range of operating temperatures. I have an older Shindaiwa string trimmer that my "small engine guy" (also my brother) told me to only use a certain type of 2-cycle oil because of its high top-end operating temperature. I had asked him because I had plenty of Mercury 2-cycle oil and I wondered if I could use it in my trimmer gas.

                Another possible reason is the difference in the range of RPMs between the two engines - the smaller engines probably idle slower, but top out higher. The higher ratio might be more of a fit for faster moving parts.

                There may be other reasons, too, but those are two that come to mind for me.

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