Mercury 75 Service Manual page 117

MAXIMUM TIMING
1. Hold control arm against maximum advance
stop. 1994/1995 Models – Crank engine with
starter motor and adjust maximum advance
screw to align 22 BTDC mark on flywheel with
timing pointer (due to the advance characteristics
of ignition system, this cranking speed adjust-
ment will automatically be reduced to 20 BTDC
at engine speed of 3000 RPM). Tighten locknut.
1996/97/98 Models – Crank engine with starter
motor and adjust maximum advance screw to
align 25 BTDC mark on flywheel with timing
pointer (due to the advance characteristics of ig-
nition system, this cranking speed adjustment
will automatically be reduced to 23 BTDC at en-
gine speed of 3000 RPM). Tighten locknut.
a
a - Control Arm
b - Maximum Advance Screw
c - Locknut
2C-8 - ELECTRICAL
c
b
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INITIAL STARTING ADJUSTMENTS
NOTE: For adjusting carburetor throttle linkage and
synchronizing carburetors, see section "Timing/
Synchronizing/Adjusting" of this manual.
After service or replacement of carburetor, turn low
speed mixture screw adjustment in (clockwise) until
it seats lightly, then back off (each carburetor) to
specifications (80 JET/100/115/125 - 1-1/2 turns).
This will permit engine start-up.
LOW SPEED MIXTURE ADJUSTMENTS
NOTE: Only the top two carburetors on four cylinder
models have an adjustable low speed mixture screw.
1. Start engine and allow to warm up (run for several
minutes). Throttle back to idle for about one min-
ute to allow RPM to stabilize.
2. With engine running at idle speed (in water) in
"Forward" gear (prop on), turn low speed mixture
screw, IN (clockwise) until engine starts to "bog"
down and misfire. Back out 1/4 turn or more.
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.
a
a - Low Speed Mixture Screw
90-830234R3 DECEMBER 1997
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