1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 100Get this manual
PROBLEM 1: ENGINE IDLES ROUGH AND STALLS PROBLEM 2: ENGINE RUNS UNEVEN OR SURGES PROBLEM 3: ENGINE WILL NOT ACCELERATE Possible Cause Corrective Action Fuel tank air vent closed CheckAir vent must or restrictedbe open all-the-way and free from restrictionsA pinched, cut or Check all fuel lines and restricted fuel line; also replace as neededloose fuel line Check and tighten all connectionfuel line connectionsA dirty or restricted fuel filterRestricted filter in fuel tankCheck, replace, or clean all fuel filtersClean by rinsing in clean lead-free gasoline or keroseneCheck fuel and replace, if necessary A crack in the fuel outlet tube (located in fuel tank Anti-Siphon valve restricting fuel flow
Replace
Refer to "Checking for Restricted Fuel Flow Caused by Anti-Siphon Valves," following
PROBLEM: FUEL BLOW-BACK OUT OF CARBURETOR Possible Cause ChippedBroken (reed-block) Reeds Corrective Action Replace Reeds