Mercury Mariner V-250 V-275 Outboard Service Shop Manual 1990, Page 77Get this manual
PROBLEM 1: Engine Idles and Stalls PROBLEM 2: Engine HesitateUpon AccelerationPROBLEM 3: Engine RunUneyen or Surges
Improperly mixed fuelContaminants (water, dirt, etc) in fuelFuel tank air vent closed or restricted pinched, cut or restricted fuel lineAlso loose fuel line con nectionA dirty or restricted fuel filterLow fuel pump pressureAn anti-siphon valveA needle and seat (in carburetor) that is either stuck open or closed (A needle and seatthat is stuck open, will cause flooding conditionA needle and seat, that is stuck closedwill prevent fuel from entering carburetor Im proper carburetor jets or restricted jetImproper carburetor float levelCarburetor loose on reed block housing Reed block housing loose, or gaskets are defective
Check fuel in fuel tank and replace if necessaryCheck air vent on fuel tankAir vent must be open all-theway and free from restriction Check all fuel lines and replace as neededCheck and tighten all fuel line connectionsCheck and replace or clean all tuelliltersRefer to "Testingin this sectionRefer to "Checking for Restricted Fuel Flow" in this section Refer to "Carburetor Adjustments" in this section