1988 Johnson/Evinrude "CC" 40 thru 55 Models Service Manual, Page 88Get this manual
AccuMixTM AccuMix is an oil injection system that delivers constant 100: 1
fueloil ratio to the engine at all speedsFuel Tank Drain and flush the tank at least once year, and at every tune-up or major repairDrain tank at an outdoor location, away from all possible sources of ignitionAnyone of the oil reservoir screws can be removed to drain fuel from the tankClean the tank by flushing with clear gasoline or mild solvent
Cleaning, 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 body
i even though these materials are sold as being suitable for
Never apply patching materials to an outboard fuel tank