1981 Johnson/Evinrude 4HP Outboards Service Manual, Page 14Get this manual
ENGINE FUEL AND LUBRICANT RECOMMENDED GASOLINE: Use gasoline with the following minimum octane numbersANTI-KNOCK INDEX NUMBER Number posted on gasoline pumpRESEARCH OCTANE NUMBER (RON) Most commonly used in the past67 69
BELOW 32F (OC)Follow ABOVE 32F (OC) mixing instructionsAdditional mixing is required by thoroughly shaking tank
SAFETY WARNING
Gasoline is extremely flammable and highly explosive under certain conditionsAlways stop engine, and do not smoke or allow open flames or spark near the boat when refueling or changing fuel tanksFUEL MIXTURE part lubricant to 50 parts gasoline or: (1 Galcontainer) 2.7 floz(80 mL) lubricant to gallon (3.8 litres) of gasoline(2.5 Galcontainer) 6.7 floz(200 mL) lubricant to 2.5 gallons (9.5 litres) of gasoline(3 Galcontainer) 12 pint (240 mL) lubricant to gallons (11.4 litres) of gasolineIMPORTANT: Additive compounds such as "tune-up" compounds,tonics," "friction reducing compounds, etc are unnecessary and are not recommendedThe use of OMC Engine Cleaner (OMC Engine Tuner), OMC Rust Preventive Oil (OMC Storage Fogging Oil) and OMC 2+4 Fuel Conditioner is recommended