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O/T outboard motor

Discussion in 'Off Topic Threads' started by fcd67, Jun 5, 2012.

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  1. fcd67

    fcd67 Member

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    Just got an old 15 hp Johnson from my father in law. Never had an outboard before. He didn't remember the gas to oil ratio. One friend told me 50:1 another told me 25:1. So which is it?
    Thanks
    Sean
     
  2. Jim101

    Jim101 Active Member

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    How old is the engine?

    Jim
     
  3. chuckie68

    chuckie68 Active Member

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    I have a 1989 Evinrude (same motor) and at that time they were already 50:1.

    Chuck
     
  4. chuckie68

    chuckie68 Active Member

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    I have a 1989 Evinrude (same motor) and at that time they were already 50:1.

    Chuck
     
  5. Jim101

    Jim101 Active Member

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    Assuming it's water cooled and at least a 1960 model run it at 50:1, You can run it 25:1 but take a case of spark plugs and a respirator with you.


    Jim
     
  6. trim tab

    trim tab Active Member

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    50-1 is it
     
  7. CalvinMD

    CalvinMD Well-Known Member

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    I use Amsoil synthetic...run it 100:1 as directed..lot less smoke and runs smoother..( mine is a 140 V4 Johnson thats a 50:1 with regular oil)..It seems expensive per bottle but works out near the same
     
  8. Tron

    Tron Supporting Vendor Supporting Vendor

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    Calvin, if I were you, I would stop running the 100:1 ratio on OMC products. There was a program on the late 80's to early 90's motors that they would inspect and replace the power heads if needed, remove the 100:1 ratio stickers on the sides of the motor and slap a 50:1 sticker in it's place.

    50:1 it is.
     
  9. halfmile

    halfmile Well-Known Member

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    The following is generally true: 1958 and prior used 20:1, 1959 thru 1963 used 24:1, 1964 and newer use 50:1. High performance usage (racing) requires a ratio of 25:1. New engine break-in (not DI) requires 25:1.

    If it's a Maroon one better chase down the date of manufacture.

    FYI 20: 1 is a quart to 5 gallons, 24:1, 6 gallons.


    HM
     
  10. fcd67

    fcd67 Member

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    Thanks for all the info.
    Sean
     
  11. oz

    oz Active Member

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    same as motorcycles & chainsaws. I use motorcycle racing oil 50/1.
     
  12. Rebel Sympathy

    Rebel Sympathy Well-Known Member

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    In 1957, the Johnson 15 was replaced by the famous 18 (the DC-3 of outboards). If your 15 is of that vintage (pre 1957), then run 24/25:1, which is approximately 6oz oil per gallon of gasoline.

    A new low profile 15 came out about 1974. It was the same physical size as a 9.9. Those motors were 50:1 ratio, which is 2.75oz oil per gallon of gasoline.

    100:1 was one of a few tragic mistakes by OMC in the 1980's. Don't go to 100:1 unless you do nothing but run your engine at idle speed.

    It will not hurt a 50:1 engine to run it with a 24/25:1 ratio mix, i.e., twice the oil. Perhaps if you idle all the time, you might fowl up a plug, but the plugs should quickly "burn off" clean once the throttle is opened up for a few seconds.

    Mike
     
  13. CalvinMD

    CalvinMD Well-Known Member

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    Thanks Tron...my brothers have gotten on the water with it way more than me since I got sick...looking forward to weting a line soon though
     
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