1986+ Mercury 6/8/9.9/10/15HP 2-stroke Factory Service Manual, Page 27Get this manual
MAINTENANCE
Storage Preparations
Fuel System
IMPORTANT: Gasoline containing alcohol (ethanol or methanol) can cause formation of acid during storage and can damage the fuel systemIf the gasoline being used contains alcohol, It is advisable to drain as much of the remaining gasoline as possible from the fuel tank, remote fuel line, and engine fuel systemFill the fuel system (tank, hoses, fuel pumps, and fuel injection systems) with treated (stabilized) fuel to help prevent formation of varnish and gumProceed with following instructions1Portable fuel tank Pour the required amount of fuel systemstabilizer concentrate (follow instructions on container) into fuel tankTip fuel tank back and forth to mix stabilizer with the fuel2Permanently Installed Fuel Tank Pour the required amount of fuel systemstabilizer concentrate (follow instructions on container) into separate container and mix with approximately one liter (one quart) of gasolinePour mixture into fuel tank3Place the outboard in water or connect flushing attachmentRun the engine for ten minutes to allow treated fuel to fill the fuel system