Mercury 100 FourStroke, Service Manual

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90-830234R3 DECEMBER 1997 ELECTRICAL - 2C-3
TIMING ADJUSTMENTS
CAUTION
Engine is timed while cranking engine with start-
er motor. To prevent engine from starting when
being cranked, all spark plugs must be removed,
except no. 1 (top) cylinder plug.
IDLE TIMING ADJUSTMENT
1. Connect timing light to no. 1 (top) spark plug.
WARNING
Before cranking engine, keep clear of propeller
as it may rotate.
2. Shift engine to “Neutral”.
IMPORTANT: To accurately time engine at crank-
ing speed, a fully charged battery must be used.
3. Holding throttle arm at idle position, crank engine
with starter motor and adjust idle timing screw to
align 5
°
BTDC timing mark of flywheel with timing
pointer. Tighten locknut.
20442
a
2
°
- 8
°
BTDC
0 2 8
a - Idle Timing Screw
MAXIMUM TIMING
1. Hold control arm so that maximum spark ad-
vance screw is against stop.
2. Crank engine with starter motor and adjust maxi-
mum spark advance screw to align the specified
BTDC timing mark on flywheel with timing pointer
(due to the advance characteristic of this ignition
system, this cranking speed adjustment will auto-
matically be reduced by 2
°
at an engine speed of
3000 RPM). Tighten locknut.
53419
a
b
c
a - Control Arm
b - Maximum Spark Advance Screw
c - Locknut
MAXIMUM THROTTLE
1. Hold throttle arm against full throttle stop screw.
Adjust full throttle stop screw to allow throttle
shutters to open fully, then turn stop screw in
(clockwise) an additional 1/2 turn, to prevent
throttle lever of center carburetor from acting as
a stop. Tighten locknut.
53420
a
b
c
a - Throttle Arm
b - Full Throttle Stop Screw
c - Locknut