1979 Evinrude 4 HP Outboards Service Manual, PN 5424, Page 16Get this manual
TROUBLE CHECK CHART (CONT) TROUBLE POSSI BlE CAUSE POWERHEADSee Section Carburetor and magneto not synchronized Throttl control lever won 't advan ce Air leak at manifold gasketswarped manifo ld (backfires) Broken leaf valves (backfires) Excessive carbon on pistons and cyl inder head Stuck piston, rings, or scored cyl ind er BCARBURET ORSee Section Poor fuel mitoo much lubricant Carburetor adjustments(too leanbackfires) (too richexcessive fuel) Choke not operat ng properl Air leaks at pocking nuts or core plugs Inlet need le and sea worn or sticky In correct carburetor float se tting AI ti tude horsepower loss CFUEL TANSee Section Faulty fuel hose (poor clamps or seals) Fuel fil ter restricted Shut-off valve not open Vent screw not open Valves not operating DEXHAUST GAS ENTERI NG CARBURETORSee Section Ex haust cover screws leak ng Cover plate gasket damaged Exhaust re ief obstructed lower motor cover to exhaust housing gasket leaking Cracked exha ust housing Exhaust housing to lower motor cover screws loose or missing EOVERHEATI NG POWER HEADSee Section lower motor cover to powerhead gasket mproperl nsta ll ed or damaged Head gasket leaking (warped cylinder head) (water in cyl inders) Water intakes obstructed Pump hou sing air bl eed restricted Water passages or tube obstructed Pump impe ller plate worn Pump impeller damaged Pump impe Ier housi ng cup worn Pump housing seal worn (driveshaft grooved) Water tube imprope rl install ed Pump housing grommet leaks FlOWER UNITSee Section Propeller hub slipping Bent or worn propel Ier Exhaust outlet damaged or clogged Ben gear hou si ng or exhaust housing (broken driveshafts) Be nt propeller (vibration) GEXHAUST GASES ENTERI NG COOLI NG SYSTEM See Section Pump pi ate not sea ng (bottom) Damaged water tube grommet or "a" ring Pump housing seal damaged (5" adapter sea ls) Exhaust outl et gasket missing Ex haust housing gasket damaged A