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  1. #1

    Default 1985 Evinrude 9.9hp 2-stroke, 50:1 or 100:1 oil?

    Hi all,

    I have a 1985 Evinrude 9.9hp short shaft two stroke here. I believe its model number starts in either E10 or 10E. There is a sticker on the powerhead cover next to the fuel line connection which shows a few cartoon icons of a gas can, and oil drop, showing a ratio of 100:1 for the fuel:oil.

    My questions are:

    1) Isn't this thing too old to be using a 100:1 oil ratio? I thought outboards that were 20+ years old all used 50:1?

    2) Is there any possibility that somebody put this sticker on the motor some time in the last 25 years without knowing what ratio it really needs? The sticker has a clear background and is located very close to the fuel line connection. It seems to me like something that was factory original but I am not certain.

    I know that using 50:1 in a 100:1 motor can result in clogging which requires disassembly and cleaning, but that it won't generally harm the engine long term. However I've read horror stories of using 100:1 in motors that need 50:1 which will cause permanent damage. Please help me avoid screwing up my motor...

  2. #2
    Vice Admiral 1946Zephyr's Avatar
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    Default Re: 1985 Evinrude 9.9hp 2-stroke, 50:1 or 100:1 oil?

    Ignore anything that says 100:1 It was the mid 80's, when OMC tried to make their two stroke outboards run on 100:1 mix and they ended up having a huge recall and doing rebuilds and powerhead replacements. I picked up a 1986 25hp Evinrude that benefited from this recall and got a new powerhead. So, the best thing to do is, stay with the 50:1 mix instead.
    Vice Admiral Zephyr

    1941 Johnson HD-20 (in restoration)
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  3. #3
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    Default Re: 1985 Evinrude 9.9hp 2-stroke, 50:1 or 100:1 oil?

    1985 was the 1st year that they tried 100:1 fuel mixes
    They switched back to 50:1 after 2 or 3 years. The old 100:1 stickers should have been removed and the instruction books amended.

    However if it runs OK dont worry but use 50:1.

  4. #4

    Default Re: 1985 Evinrude 9.9hp 2-stroke, 50:1 or 100:1 oil?

    I have a 1986 Evinrude 15 i bought used in `89. It also had that same sticker calling for 100:1. I always ran 50:1 in it and later bought a shop manual. The manual said to run 50:1.

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