Mercury 35/40HP 2 Cylinder Outboards Service Manual PN 90-42794--1, Page 58Get this manual
CHECKING FOR RESTRICTED FUEL FLOW CAUSED BY ANTI-SIPHON VALVES While anti-siphon valves may be helpful from safety stand-point, they clog with debris, they may be too small, or they may have too heavy springSummarizing the pressure drop across these valves can, and often does, create operational problems andor powerhead damage by restricting fuel to the fuel pump and carburetor(s) Some symptoms of restricted (lean) fuel flow, which could be caused by use of an anti-siphon valve, are: 123456789Loss of fuel pump pressure Loss of power High speed surging Preignitiondetonation (piston dome erosion) Outboard cuts out or hesitates upon acceleration Outboard runs rough Outboard quits and cannot be restarted Outboard will not start Vapor lock
Troubleshooting Fuel Pump
PROBLEM: AIR BUBBLES IN FUEL LINE
Possible Cause Low fuel in fuel tank Loose fuel line connection hole or cut in fuel lineCorrective Action Fill tank with fuelCheck and tighten all connectionsCheck condition of all fuel lines and replace any found to be badTighten all screws evenly and securelyRebuild fuel pump