1988 Johnson Evinrude "CC" 9.9 thru 30 Service Manual, P/N 507660, Page 83Get this manual
Fuel Tank
i tune-up or major repairDram tank at an outdoor
Drain and flush
least .once year, and at every
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 bodyCOA1999