1984-1986 Mercury Force 9.9 and 15HP Outboards Service Manual, Page 17Get this manual
It is most likely the engine ill have to be run for few moments with the choke in operation until the engine warms up Intermediate Oper ation, Engine speed and air lIow increase as the throttle shutter opens The secondary idle discharge ports are progressively exposed to low engine pressure which dr aws luellrom the main nozzle well through the idle tube into the bypass chamber and discharges it into the engineAs throttle continues to open the air lIow incr easesThe higher air flow creates lower press ure around the main nozzle allowing more fuel to flow from the bowl (high pr essure area) to carburetor throat (low pressure area)Throttle positio determines the quantity of intermediate luel delivered from the main nozzle which mixes downstream with the existing intermed iate and Id le fuel already flowing in the system Figure 3Idle Operation, During idle operation air is moving thru the carburetor throat at low vol ume and speed This slow air flow does not create enough vacuum (low pressu e) to lift luel from the large opening 01 the main nozzlebut is able to liftluel thru the smal ler idle tubeAs luel is lifted from the idle fuel tube, it is atomized by air from the idle air bleed passage It then passes through the idle adjustment orifice into the by-pass ch amber ixing ith additional air supplied through the secondary id le ports and discharges into the throttle bore through the primary idle discharge portFigure2