1978 Johnson 175, 200, 235 HP Outboard Service Manual, Page 23Get this manual
LEAF VALVES The leaf valves time the injection of the fuel mixture into the crankcase by opening only when the pressure in the crankcase has dropped to predetermined point on the compression strokeThe leaf is so designed that it maintains constant contact with the leaf plate, and will spring away from the plate when predetermined pressure is exerted against itLeaf travel away from the plate is limited by the leaf stopWhen pressure is removed, the inherent spring action of the segments returns and holds them against the plateCHOKE AND CHOKE SOLENOID The carburetors are fitted with an electric chokeThe choke may be manually operatedWith the choke lever in the "OFF" position, the choke valve is held in fixed open position, allowing air to pass freely through the inletWith the choke lever in the "ON" position, the valve is held in closed position, restricting the flow of air to the carburetorWith the choke lever in "OFF" position, if full choking is required, the ignition key switch can be operated to fully energize the choke solenoid nate suction and pressure in the crankcase are transmitted to the pump diaphragmSuction created on the upward stroke of the piston causes the diaphragm to displace and draw in fuel through the inlet val veOn the following downward stroke of the piston, crankcase pressure flexes the diaphragm in the oppOSite directionThe inlet valve is then seated, pre- venting the return of fuel to the tank, while the discharge valve is opened, allowing fuel to pass to thecarburetorFuel is drawn through fine filter screen before entering the pump to remove impuritiesSee Figure 3-2FUEL TANK The fuel tank is non-pressurized, suction operated tankFuel is lifted from the tank to the carburetor by the fuel pumpsPriming is achieved by squeezing the primer bulb (part of the fuel line) several times or until pressure resistance to squeeze the bulb increasesSee Figure 3-3