2004 SR Johnson 2 Stroke 9.9, 15, 25, 30 HP Outboards Service Manual, Page 142Get this manual
FUEL SYSTEM COMPONENTS
Carburetor
The carburetor meters and distributes the fuel to the engineIt controls engine speed and power output by varying the intake charge densityTo react correctly to wide range of operating conditionsthe carburetor has multiple fuel mixing circuitsFuel mixture enrichment for cold starting is controlled by either choke (9.915 Models) manual primer (25 TE and 2530 Models)or fuel primer solenoid (Remote Electric Models)
Intake Manifold
The intake manifold provides the mounting surfaces to adapt the carburetor to the cylindercrankcase assemblyIt contains the leaf valves which control the intake charge to each cylinder