Mercury 40 Service Manual page 126

TIMING, SYNCHRONIZING, & ADJUSTING
Carburetor Synchronization – Dynamic Adjustment
NOTE: The carburetors are synchronized by adjusting the intake manifold vacuum on the
top three carburetors. Use Carburetor Tuner (91-809641A1) to measure the vacuum.
NOTE: The engine should be completely warmed up for the adjustment. Correct adjust-
ments can not be obtained in a cold condition.
INSTALLING CARBURETOR TUNER (91-809641A1)
1. Remove four plugs from the intake manifold.
2. Install a intake manifold hose adaptor in each plug hole.
NOTE: Intake manifold hose adaptors are provided with the Carburetor Tuner.
3. Connect the carburetor tuner to the hose adaptors.
a
b
a -
b -
c -
d -
To avoid the possibility of drawing mercury from the vacuum gauge into the engine,
do not run engine at high rpm speed and avoid rapid throttle deceleration (high vac-
uum situations).
SYNCHRONIZING CARBURETORS
1. With the outboard in water, start engine and allow to warm up. Shift the outboard to neu-
tral.
2. Connect a tachometer to the engine.
3. Adjust idle rpm screw (a) on #4 carburetor to obtain an idle setting of approximately1000
rpm in neutral. If necessary, keep adjusting the idle screw.
Page 2C-4
Intake Manifold Plugs (4)
Intake Manifold Hose Adaptor (4)
Filters (35-18206)
Carburetor Tuner (91-809641A1)
c
d
CAUTION
90-828631R3 MARCH 1999