1997+ Mercury 35/40HP 2 Cylinder Outboards Service Manual PN 90-826148R2, Page 157Get this manual
Problem: Engine Floods Possible Cause Dirt or debris are preventing inlet needle from seatingWorn inlet needlePunctured float Incorrect float setting Problem: Engine Runs Too Rich Possible Cause Fuel level too highCarburetor floodsIdle nozzle air holes pluggedRestricted air flowMain fuel jet looseProblem: Fuel Blow back Out of Carburetor Problem: Unable to Reduce Engine RPM to Slow Idle Possible Cause Chipped or broken reeds on reed blockProblem: Rough Idle Possible Cause Excessive pre-load on reedsProblem: Engine Runs Too Lean Possible Cause Carburetor is looseAir leaks past mixing chamber coverFuel level is too lowClogged high speed jetRestricted fuel flow to carburetorIncorrect high speed jetIdle mixture set too leanAir leakage into fuel systemCorrective Action Tighten bolts securelyTighten cover or replace gasketReset float levelInspect jet for varnish or debris and cleanCheck fuel lines and filter(s) for restricted flowRefer to main jet chart and replace with proper jetAdjust to run richer (turn idle mix screw counterclockwise)Inspect fuel line connections, hose clamps, fuel pump and fuel outlet tube (located in fuel tank) for loose fittingsRefer to Section 3B for checking for restriction of fuel flow caused by anti-siphon valveReplace reedsCorrective Action Replace reedsCorrective Action Corrective Action Reset float to correct levelSee preceding "Engine Floods Blow out with compressed airInspect cowl air inlet and carburetor for obstructionsRe-tighten jetCorrective Action Flush out inlet seat and clean inlet needleReplace ReplaceReset float Anti-siphon valve restricting fuel flow