1981 Johnson/Evinrude 4HP Outboards Service Manual, Page 16Get this manual
TROUBLE CHECK CHART TROUBLE POSSIBLE CAUSE AFUEL SYSTEMSee Section Fuel valve shut off Speed control not advanced (throttle closed) Engine flooded Old fuel Clogged fuel filter Choke not closing completely Fuel system foul ty IGNITION SYSTEMSee Section Throttle cam improperly adjusted Spark plug leads crossed or reversed Sheared fl ywheel key Ignition system faul ty POWERHEADSee Section Carburetor and magneto not synchronized Throttle control lever won't advance Air leak at manifold gasketswarped manifold (backfires) Broken leaf valves (backfires) Excessive carbon on pistons and cyl inder head Stuck piston, rings, or scored cyl inder CARBURET ORSee Section Poor fuel mixtoo much lubricant Carburetor adjustments(too leanbackfires) (too richexcessive fuel) Choke not operating properl Air leaks at packing nuts or core plugs Inlet needle and seat worn or sticky Incorrect carburetor float setting Altitude or temperature horsepower loss FUEL TANKSee Section Faulty fuel hose (poor clamps or seal s) Fuel filter restricted Shut-off valve not open Vent screw not open EXHAUST GAS ENTERI NG CARBURETORSee Section Exhaust cover sc rews leaking Cover plate gasket damaged Ex haust rei ief obstructed Cracked exhaust housing OVERHEATING POWERHEADSee Section Head gasket leaking (warped cyl inder head) {water in cyl inders} Water intakes obstructed Pump housing air bleed restricted Water passages or tube obstructed Pump impel Ier pi ate worn Pump impeller damoged Pump impeller housing cup worn Pump housing seal worn {driveshaft grooved} Water tube improperly installed Pump housing grommet leaks LOWER UNITSee Section Propeller hub slipping Bent or worn propel Ier Exhaust outlet damaged or clogged Bent gear housi ng or exhaust housing {broken driveshafts} Bent propeller {vibration}