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  1. #1
    rws is offline
    Registered rws's Avatar
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    Jan 2001
    Toledo Ohio Eubank Ky

    Mercury Outboard Oil Mix Ratio?

    This is a question for the Outboard Guys.
    My Friend has a pair of 99 280 Hp. Mercs, He is running Klotz synthetic oil at a 32 to 1 ratio . I think this mixture is excessive for a synthetic oil.I used to run 80 to 1 in snowmobiles. What oil and ratios do you in your Mercury outboards?


  2. #2
    Platinum Member Platinum Member mcollinstn's Avatar
    My Boats:
    1991 F311SR1
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    Sep 2001
    I ran 50:1 in all my pleasure motors. I ran 32:1 in all my dragrace motors.

    Whatever ratio his Merc manuals specify should be fine with a premium oil. Be sure to note that changing ratios changes carburetor jetting.
    I see London, I see France...

  3. #3
    Charter Member #232 Charter Member Audiofn's Avatar
    My Boats:
    1979 Formula 302, 99 Formula 353, 81 Donzi 18 2+3 with 454
    Join Date
    Oct 2000
    Carlisle, MA USA
    at 280 I assume these are 2.5 efi's. I would not thin them out at all. Better to run them with plenty of oil then not enough. Cheap insurance if you ask me

    Put your best foot forward!

  4. #4
    My Boats:
    '77 Martini 7 Meter
    Join Date
    Feb 2002
    Honeoye, NY
    More oil is not always better!! Oil mixed with gas and then burned is the final fuel. On a 2/cyl., oil passes through the crankcase with gas and maintains a healthy lower end. The least amount of oil needed to lubricate the crankcase is what you want. More oil than needed lowers the octane of the fuel you burn leading to detonation. I have always found that a really good synthetic (I use AMSOIL mixed at 75 to 100/1) will give you max. performance at even over recommended RPM's, burn clean, and keep the engine very healthy. --- Jer

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