Mercury 225 EFI, Service Manual

Page: 148 / 719

TIMING, SYNCHRONIZING & ADJUSTING
Page 2C-4 90-884294 OCTOBER 2001
Timing
All timing adjustments are controlled by the Electronic Control Module (ECM). No external
mechanical timing adjustments can be made.
Actual engine timing can be monitored by using a Digital Diagnostic Terminal (DDT).
Ignition timing at idle, whether in gear or in neutral, will vary.
The ECM will use ignition timing to maintain an rpm of approximately 700 in neutral and
625 in forward gear. An engine that is cold will require more timing advance than an engine
that is at normal operating temperature.
Engine timing at idle should be between 0
°
to 6
°
BTDC with the engine at normal operating
temperature.
Engine timing at 5000 rpm should be approximately 22
°
BTDC for all models.
Maximum Throttle Adjustment
1. Hold throttle arm against full throttle stop screw. Adjust full throttle stop screw to allow
full throttle valve opening, while maintaining a clearance of 0.020 in. (0.50 mm) be-
tween arm of throttle shaft and stop on throttle assembly. Tighten locknut.
2. Check for slight free play (roller lifter from cam) between roller and cam at full throttle
to prevent linkage from binding. Readjust full throttle stop screw, if necessary.
0.020 in.
(0.050 mm)
c
d
b
a
e
59032
a - Throttle Arm
b - Full Throttle Stop
Screw
c - Throttle Shaft Arm
d - Stop
e - Locknut