Carburetor Adjustments; Initial Starting Adjustment; Idle Speed Adjustment; Idle Mixture Screw Adjustment - Mercury 45 Jet 50-55 Service Manual

Carburetor Adjustments

INITIAL STARTING ADJUSTMENT

Turn idle mixture screw in (clockwise) until it seats LIGHT-
LY--then back-off (each carburetor) 1-1/4 turns.
IDLE SEED ADJUSTMENT
1. Adjust engine idle RPM as outlined in Section 2C
"Timing/Synchronizing/Adjusting."

IDLE MIXTURE SCREW ADJUSTMENT

1. Start engine and allow to warm-up. Throttle back en-
gine to idle for about one minute.
2. With engine running at idle speed in "Forward" gear --
turn idle mixture screw IN (clockwise) until engine
starts to "bog" down and misfire. Back out 1/4 turn or
more.
a
a - Idle Mixture Screw (on each carburetor)
3. Check for too lean mixture on acceleration.
4. DO NOT adjust leaner than necessary to attain rea-
sonably smooth idling. When in doubt, stay on the
slightly rich side of the adjustment.
90-817643R1 DECEMBER 1996

CARBURETOR FLOAT ADJUSTMENT

1. Remove carburetor as outlined in "Carburetor Remov-
al," following.
2. Remove fuel bowl and gasket and check float level us-
ing a carburetor scale.
3. If necessary, adjust float level by bending metal tab (on
float) to which inlet needle is clipped.
9/16 (14.3mm)
a
b
a - Metal Tab
b - Inlet Needle

MAIN (HIGH SPEED) JET ADJUSTMENT

The carburetor has a fixed high speed jet. Extreme
changes in weather (temperature and humidity) and/or ele-
vation may result in a too lean or rich fuel mixture at wide-
open-throttle, which may require a change in the high
speed jet. A smaller size main jet will lean the fuel mixture,
and a larger size jet will enrich the fuel mixture.
50555
a - High Speed Jet
b - Bowl Drain Plug
c - Bowl Vent Jet
d - Idle Mixture Screw
51046
d
c
a
b
51118
FUEL SYSTEMS - 3A-11