1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 99Get this manual
Carburetion Fuel System Troubleshooting
Troubles, that are caused by items 1-thru-5, listed below, may give the impression that problem exists in the fuel system: 1Spark plugs 2Ignition spark voltage 3Cylinder compression 4Reed valves 5Ignition timing
PROBLEM: ENGINE FLOODS Possible Cause Dirt or foreign particles are preventing inlet needle from seatingWorn inlet needlePunctured floatIncorrect float settingCorrective Action Flush out inlet seat and clean inlet needleReplaceReplaceReset float
PROBLEM: ENGINE RUNS TOO LEAN Possible Cause Carburetor is looseAir leaks past mixing chamber coverFuel level too lowClogged high speed jetRestricted fuel flow to carburetorIncorrect high speed jetCorrective Action Tighten bolts securelyTighten cover or replace gasketReset float levelCheck and cleanCheck fuel lines and filter(s) for restricted flowRefer to main jet chart and replace with proper jetAdjust to run richenerCheck fuel line connections, hose clamps, fuel pump, and fuel outlet tube (located in fuel tank) for loose fittingsRefer to "Checking for restricted fuel flow caused by Anti-Siphon valves