THUNDERBOLT IV AND V IGNITION SYSTEM - 4B-1990-823225--1 1096
Timing and Idle Adjustment
Procedures For Thunderbolt
V Ignition
Setting Base Ignition Timing
1. Connect timing light to number 1 spark plug.
Connect timing light power supply leads (if
applicable) to 12 volt source.
2. Connect a shop tachometer to engine.
3. Using a jumper wire, connect the ignition system
timing lead “13” (PUR/WHT wire) to a good en-
gine ground (–). This locks the ignition module
into the “Base Timing Mode”.
4. Start engine and run at normal idle speed. Allow
engine to reach normal operating temperature.
5. Aim timing light at timing tab, located on the tim-
ing gear cover and crankshaft torsional damper.
6. Adjust timing using the conventional method.
IMPORTANT: Be sure to disconnect the jumper
wire from the ignition system test terminal before
attempting to resume normal operations. If the
jumper wire is left in place, the ignition module
will operate in the “Base Timing Mode”. This
means that the additional timing advance fea-
tures would not function.
7. Make sure that the distributor has been tight-
ened. Remove the jumper wire from the timing
terminal.
8. Stop engine and remove timing light.
Adjusting Idle Mixture
The procedure for adjusting carburetor idle mixture
can be found in the appropriate engine service manu-
al. This procedure also requires that the ignition mod-
ule be locked in the “Base Timing Mode”.
IMPORTANT: In order to properly set idle mixture,
the ignition module MUST BE locked in the “Base
Timing Mode”. This is necessary because of the
“Idle Speed Control” feature that exists in the
ignition module. See information on the previous
pages about this feature.
1. Using a jumper wire, connect the ignition system
timing lead “13” (PUR/WHT wire) to a good en-
gine ground (–). This locks the ignition module
into the “Base Timing Mode”.
2. Adjust idle mixture following the procedure in the
appropriate engine service manual.
3. Remove the jumper wire from the timing terminal.
Adjusting Engine Idle Speed
This procedure should be done with boat in the water,
drive unit in neutral and engine at normal operating
temperature. Refer to the Operation and Mainte-
nance Manual for the correct idle speed.
1. Disconnect the throttle cable from carburetor.
IMPORTANT: In order to properly set idle speed,
the ignition module MUST BE locked in the “Base
Timing Mode”. This is necessary because of the
“Idle Speed Control” feature that exists in the
ignition module. See information on the previous
pages about this feature.
2. Connect a shop tachometer to engine.
3. Using a jumper wire, connect the ignition system
timing lead “13” (PUR/WHT wire) to a good en-
gine ground (–). This locks the ignition module
into the “Base Timing Mode”.
4. Start engine and allow it to reach normal operat-
ing temperature.
5. Adjust idle speed to recommended RPM.
6. Stop engine. Readjust cable barrel and reinstall
the throttle.
IMPORTANT: Be sure to disconnect the jumper
wire from the ignition system test terminal before
attempting to resume normal operations. If the
jumper wire is left in place, the ignition module
will operate in the “Base Timing Mode”. This
means that the additional timing advance fea-
tures would not be functioning.
7. Remove the jumper wire from the timing terminal.
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