1988 Johnson/Evinrude "CC" 40 thru 55 Models Service Manual, Page 82Get this manual
Fuel Tank L!J
Drain and flush tank least.once year, and at every tune-up or major repairDram tank at an outdoor location, away from all possible sources of ignitionA drain screw is provided in the fuel tank upper housingClean the tank by flushing with clear gasoline or solventPrimer pump, screens, etc may be inspected and cleaned as described belowRefill the tank with the correct fuel mixtureCleaning, Inspection and Repair If the tank or hose appears to be leaking fuel or fumes, pressure test tank and hose assembly before doing any disassemblyClean the fuel tank and inspect for rust or leakageReplace tank if badly rusted or if it has developed leaks in the metal bodyNever apply patching materials to an outboard fuel tank even though these materials are sold as being suitable for fuel tank repairGenerally, these materials are sold for repairing automotive fuel tanks and are not suitable for portable marine tanks which are subjected to much higher pressure and vacuum conditionNever use patched or repaired fuel tank that could allow fuel leakageIgnition of this leakage could result in fire or explosion