1978 Johnson 4HP outboards Service Manual, Page 29Get this manual
cReconnect fuel hosesTighten filter and pump screws securelyCheck for leaks by con necting fuel tank line to motor and squeezing primer bulb until definite pressure is felt in the bulb CLEANING, INSPECTION, AND REPAIR
FUEL LINE, SCREEN AND NIPPLE ASSEMBLY Disconnect the fuel hose from the tankSee "Clamps" in paragraph "Hose and Primer Bulb Assembly", Section 3Remove the fuel line, screen and nipple assemblySee Figure 3-20Inspect screen for varnish deposits and remove with OMC Accessory Engine Cleaner
FUEL TANK
FUEL MIXTURE motor in excellent mechanical and operating condition may give faulty performance because of an improper fuel mixturePetroleum gum and varnish which precipitate from stale mixture may clog the filter screen and any small orifices, interfering with starting and normal runningFor proper fuel mixtures see Engine Fuel and Lubricant, page 2-6To assure that the fuel tank contains the proper mixture, drain and flush the tank at least once year, and at every tune-up or major repairClean the tank by flushing with clear gasoline or solventPrimer, screenetc may be inspected and cleaned as described belowRefill the tank with the correct fuel mixtureDESCRIPTION