1984-1986 Mercury Force 4HP Outboards Service Manual, Page 9Get this manual
SECTION
FUEL SYSTEM
GENERAL
The fuel system includes the fuel tank, carburetor, and reed valv8Troubleshooting the fuel system and brief description of the operation 01 the system is discussed In th is subsection
The reduction 01 air pressure causes the fuel to be pushed into and mix ith the incoming air stream to form combustible alrtuel mixtureThe ai rlfuel mixture Is adm itted to the crankcase of the motor by reed type inlet valvesThe reed valve operates automaticallyopening when the pressure the crankcase is low enough so the outside pressure can overcome reed lensionFigure 1
OPERATION
The luel from the tank is gravity fed to the carburetorThe upstroke of the piston In the cylinder creates low pressure in the crankcase which draws air through the throat of the carburetorA restrIction in the throatcalled venturihas the effect of reducing air pressure and increasing air velocity