Adjustments; Idle Mixture Screw Adjustment; Idle Speed Adjustment; Float Adjustment - Mercury 40 Service Manual

Adjustments

Idle Mixture Screw Adjustment

INITIAL STARTING ADJUSTMENT
Turn idle mixture screw in (clockwise) until it seats
LIGHTLY--then back-off (each carburetor) the cor-
rect number of turns (See Specifications).
RUNNING QUALITY ADJUSTMENT
1. Position outboard at level trim. With gear case
submerged, start outboard and allow to warm up.
Throttle outboard back to idle for about one min-
ute.
2. Shift outboard into forward gear. Turn low speed
mixture "in" (clockwise) until outboard starts to
bog down and misfire. Turn mixture screw out 1/4
turn or more.
a - Top Idle Mixture Screw
b - Middle Idle Mixture Screw
c - Bottom Idle Mixture Screw
3. Check for too lean mixture on acceleration.
4. DO NOT adjust leaner than necessary to attain
reasonable smooth idling. When in doubt, stay on
the slightly rich side of the adjustment.
3B-10 - FUEL SYSTEM
a
b
c

Idle Speed Adjustment

1. Adjust engine idle RPM as outlined in Section 2C
"Timing/Synchronizing/Adjusting."

Float Adjustment

1. Remove carburetor as outlined in "Carburetor
Removal" in this section.
2. Remove fuel bowl and gasket and check float lev-
el using a carburetor scale (gasket removed).
9/16 in. (14.29 mm)
3. Attach Spring Clip on Inlet Needle to metal float
tab and place needle into its seat.
a - Metal Float Tab
b - Spring Clip
If necessary, adjust float level by bending metal
4.
tab (on float) to which inlet needle is clipped.
a - Bend Tab Here for Float Level Adjustment
52372
a
b
55883
a
90-852572R1 JANUARY 1998