2002/2003 Johnson SN/ST 2 Stroke 3.5, 6 8 HP Outboards Service Manual, PN 5005466, Page 32Get this manual
SPECIAL TOOLS AND SERVICE SPECIFICATIONS FUEL REQUIREMENTS
FUEL REQUIREMENTS
WARNING
Minimum Octane
87 (R+M)2 AKI or 90 RON
Johnson outboards have been designed to operate using the above fuels; however, be aware of the following: The boat's fuel system may have different requirements regarding the use of alcohol fuels Refer to the boat's owner guide Alcohol attracts and holds moisture that can cause corrosion of metallic parts in the fuel system Alcohol blended fuel can cause engine performance problems