How to Mix Gas on a 5Hp Evinrude Boat Motor

Written by will charpentier
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How to Mix Gas on a 5Hp Evinrude Boat Motor
Small Evinrudes use a fuel and oil mix in the tank. (toy outboard motor image by pearlguy from

Mixing the fuel and oil for a 5-horsepower Evinrude outboard motor isn't an onerous task. A two-stroke 5-horsepower Evinrude motor, like all two-stroke motors, needs a mix of gas and oil in its gas tank, since it doesn't have a separate lubrication system. You know the capacity of the gas can you'll use to fuel the motor's gas tank and, with a little bit of arithmetic, you can figure out how much oil to add to the fuel.

Skill level:

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Things you need

  • Approved gas can or gas tote.

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  1. 1

    Set the gas can on the ground at the fuel dock and fill it with the proper grade of gasoline, 87 octane. Evinrude asserts that no benefit is gained from using a fuel with a higher octane rating.

  2. 2

    Fill the gas can. Note the number of gallons you put in the container.

  3. 3

    Divide the number of gallons by the mix ratio for the motor use. While a 5-horsepower motor is unlikely to be subjected to racing conditions, the racing mix is 25 parts gasoline to 1 part oil--a full 5-gallon container, 18144gr, is properly mixed when you add 768ml of oil: 640/25=25.6, or 737gr. A similar mixture, 24 parts gasoline to 1 part oil, is required for two-stroke Evinrudes built between 1959 and 1963, a 20-to-1 mix is needed for older motors and a 50-to-1 mix for newer two-stroke motors, except those being broken in, which use a 25-to-1 mix, like a racing motor.

  4. 4

    Add the appropriate amount of oil to the gasoline container. Cap the container and shake it vigorously to distribute the oil. Agitate the container again before pouring the oil into the boat's gas tank.

Tips and warnings

  • One gallon is 3,785ml of gasoline. A 50-to-1 oil mixture equals 75.7ml per gallon.
  • Don't attempt to operate a two-stroke, 5-horsepower Evinrude motor without a gas-oil mix in the fuel tank.

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