1987 Johnson/Evinrude CU Outboards 35A thru 55 Service Manual, Page 79Get this manual
Fuel Requirements
Models 45 Comm 55 Comm35,40,48,50
Recommendation Any automotive gasoline or gasoline with no more than 10 EthanolAny automotive gasoline or gasoline with no more than 10 Ethanol
Minimum Octane Pump Posted 67 "RON" 69
Preferred Fuel: Any regular unleaded, regular leaded, or premium unleaded gasoline having the recommended octane rating and not extended with alcohol is the preferred fuelAcceptable Fuel: Any of the above gasolines with up to 10 maximum alcohol volume: 10 ETHANOL (ethyl alcohol) (may be called gasohol) METHANOL (methyl alcohol) +5 cosolvent alcohols Alcohol extended fuels may result in engine running quality problems, vapor lock or "fuel starvation" problems, or moisture absorption (phase separation) problemsIf running quality problems are experienced, switch to gasoline without alcohol as described in Preferred FuelUnacceptable Fuel: Do not use any regular unleaded, regular leaded or premium unleaded gasoline having more than 10 ETHANOL or more than METHANOL even if it contains cosolvents or corrosion inhibitor and regardless of octane ratingOMC products have been designed to operate using the Preferred Fuelor Acceptable Fuel; however, be aware of the following: aThe boat fuel system may be different regarding use of alcohol fuelsRefer to boat owner's manualbAlcohol attracts and holds moisture which may cause corrosion of metallic parts of the fuel systemcMetallic and nonmetallic parts of the entire fuel system should be inspected frequently and replaced if signs of excessive stiffness, deterioration, or corrosion of fuel leakage are found Inspect at least annually&