Mercury 40 Service Manual page 130

TIMING, SYNCHRONIZING, & ADJUSTING
DYNAMIC ADJUSTMENT (45 HP MODELS)
NOTE: CO metering equipment has to be used to accurately adjust the idle mixture screws
within the exhaust emissions limits.
1. Remove four plugs from the exhaust manifold.
2. Install a exhaust manifold hose adaptor (91-809905A1) in each plug hole.
a -
b -
c -
3. Install the CO metering equipment to the hose adaptors.
NOTE: Keep all the hose adaptors plugged that are not connected to the CO metering
equipment.
4. With engine in water, start engine and run at the recommended idle speed in neutral.
5. Check CO reading on each cylinder to verify if CO is within 4-6% range. While checking
CO readings, allow time for the readings to stabilize.
NOTE: Keep viewing the tachometer, as the engine rpm may fluctuate during adjustments.
Keep adjusting the idle rpm screw in order to keep the engine speed at 850 RPM.
6. Adjust CO as follows:
7. Remove hose adaptors and reinstall plugs.
8. Recheck carburetor synchronization.
Page 2C-8
a
c
b
Exhaust Manifold Plugs (4)
Exhaust Manifold Hose Adaptor (91-809905A1)
Plug - Hose Adaptor
Idle Speed-Neutral
950
Adjust CO starting from No. 1 cylinder.
If CO reading on any cylinder is higher than 6.0%, turn idle mixture screw clockwise
(leaner).
If CO reading on any cylinder is lower than 4.0%, turn idle mixture screw counter-
clockwise (richer).
Changes to any one cylinder can effect other cylinders, so If changes are made to
any cylinder, all previous cylinders checked must be rechecked/adjusted.
25 rpm
90-828631R3 MARCH 1999