Outboard Ignition Troubleshooting – Page 16 – Mercury Battery CD Ignitions (Points)
This section covers Mercury battery-powered CD ignition systems using breaker points. These systems rely heavily on proper battery voltage, clean connections, and distributor components for correct operation.
Mercury – Battery CD Ignitions with Points
Service Note:
Check battery voltage at approximately 3500 RPM. Maximum allowable voltage is 16 volts.
Anything above this can damage the ignition system.
Check for loose connections or a bad battery.
Maintenance-free batteries are NOT recommended.
- Clean all battery connections and engine grounds.
- Disconnect the mercury tilt switch and retest. If ignition works properly, replace the mercury switch.
- A CD tester can be used to test the CD module, distributor cap, rotor button, and spark plug wires.
- Connect a spark gap tester to the spark plug wires and check for fire on all cylinders. If some fire and others do not, suspect distributor cap, rotor, or plug wires.
- Connect a spark gap tester to the ignition coil lead and set to ~7/16". If it fires here but not at plugs, the issue is in the distributor system.
- Check voltage on white and red terminals during cranking. It MUST be at least 9.5 volts. If not, suspect battery, cables, harness, or key switch.
- Check DVA voltage on green wire to coil — should exceed 100 volts.
- Disconnect brown points wires. Turn key ON and tap wire to ground — unit should fire each time. If it does → CD module likely good → inspect points and plate.
- Test distributor firing order: Align rotor to #1, trigger spark manually. Only #1 wire should fire. If others fire → bad distributor cap.
- Perform full voltage drop test: Check voltage drop across all connections (positive and negative side). Any reading above 0.6V indicates resistance in that circuit.
Need Help Finding Parts?
Request Parts Here
Request Parts Here