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  1. #1

    Default 75hp Mercury outboard 4-cylinder 2-stroke fuel/oil mixture ration and other questions


    first i'd like to introduce myself since i'm new to this forum. My name is Jörg and i'm from Austria, Europe. I'm owning a boat since three years now and recently upgraded to an old Elan Boat with a 75hp Mercury outboard.

    Although i do own a service manual there are several questions that are not mentioned there (and it dont have a regualar users manual)

    Firstly the engine is supposed to be a 75hp 4-cylinders. So it should be model year 84-86 although i couldnt assure this with the serial number as it doesnt fit with any of the references found on the web. (Serial is 9453658)

    My questions are:

    1.) can anyone confirm that it is the engine i think it is?
    2.) what's the proper oil/gas mixture - previous owner said he used 1:25 but that seems a lot to me considering the supposed construction year
    3.) what is the current output of the power generator/coil on this engine (i'd like to operate a fairly high powered hifi an dont want to drain battery)
    4.) there's a problem with the rpm-meter. The instrument in the dashboard seems to work (needle moves for a moment when main power switch is closed) but it doesnt show the revs of the engine. where/how would i best start to search for the cause of this issue?

    Thanks in advance for your Feedback

    best regards


  2. #2

    Default Re: 75hp Mercury outboard 4-cylinder 2-stroke fuel/oil mixture ration and other questions


    ive vey just joined the Marine Engine forum today.
    i have a similar design and vintage Mercury engine (4-cyl; 75 HP; 1986)
    i have been successful using 50:1 gas-oil
    i also have the same question about the voltage/generator rating based on my interest in running a Bluetooth/amplifier

    i do own a good shop manual; I'll see what it says about your serial number
    My Mercury powers a 1972 Boston Whaler in Massachusetts (US)

    Best, Neil

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