1968 Evinrude Ski-Twin, Ski-Twin Electric 33 HP Outboards Service Manual, Page 12Get this manual
CHART (CONT) CAUSE 2LOSS OF POWER(Assuming Ignition POWER HEADSee Section Carburetor and magneto not synchronized Throttle controllever bent (won't advance) Air leak at manifold gasketswarped manifold (backfires) Broken leaf valves (backfires) Cracked carbon seal (water in cylinders) Excessive carbon pistons and cylinder head Stuck piston rings, or scored cylinder or piston Drain leaf holes restricted Leaf stops closed should open .040 (plug fouling) CARBURETORSee Section Poor fuel mixtoo much oil Carburetor adjustment(too leanbackfires) (too richexcessive fuel) Linkage screws loose Choke not operating Air leaks at packing nuts Inlet needle and seat worn or sticky Incorrect carburetor float setting Boss gasket leaking FUEL PUMP ANDSee Section Faulty fuel hose (clamps or seals) (kinked) Fuel tank or filter plugged Fuel filter restricted Fuel and vent valves not opening Valves not operating Diaphragm leaking or damaged Fuel system hoses plugged ring damaged in fuelline connector DEXHAUST GAS CARBURETORSee Section Exhaust cover screws leaking Cover plate gasket damaged Damaged exPaust housing seal Adapter gaskets leaking Cracked exhaust housing Exhaust tube to cylinder screws loose or missing POWER HEADSee Section Exhaust cover gasket leaking Inner exhaust cover leaking Power head gasket improperly installed or damaged Head gasket leaking (warped head) (water in cylinders) FLOWERSee Section Water intakes obstructed housing air bleed restricted Water passages obstructed plate not sealing (bottom) impeller damaged housing or plate worn housing seal worn (driveshaft grooved) Water tube grommet damaged GEXHAUST GASES COOLING SYSTEM See Section impeller plate not sealing (bottom) Damaged water tube grommets or rings housing seal damaged (5" adapter seals) Exhaust tube to plate gasket damaged