Outboard Ignition Troubleshooting – Page 10 – Force with Mercury Designed Ignitions (1992-1999)
This page covers Force outboards using Mercury designed ignition systems from 1992 through 1999. These procedures focus on two cylinder engines using a separate switch box and ignition coils, including stator testing, trigger testing, switch box diagnosis, and high-speed miss checks.
Force with Mercury Designed Ignitions (1992-1999)
Two Cylinder Engines Using a Separate Switch Box and Ignition Coils
No Fire At All
- Disconnect the black/yellow kill wire at the pack and retest. If the ignition now fires, the kill circuit has a fault, possibly the key switch, harness, or shift switch.
- Disconnect the yellow wires from the stator to the rectifier and retest. If the engine fires, replace the rectifier.
- Check cranking RPM. A cranking speed less than 250 RPM will not allow the system to fire properly.
- Check stator resistance and DVA output as shown below.
Motors with Black Stator
| Wire | Read To | Resistance | DVA |
|---|---|---|---|
| Blue | Blue/White | 3250-3650 | 180V or more |
| Red | Red/White | 75-90 | 25V or more |
Motors with Red Stator
| Wire | Read To | Resistance | DVA |
|---|---|---|---|
| White/Green | Green/White | 500-700 | 180V or more |
Red Stator Adapter
| Wire | Read To | Resistance | DVA |
|---|---|---|---|
| Blue | Engine Ground | Open | 180V or more |
No Fire or Intermittent on One Cylinder
- If the cylinders only act up above idle, connect an inductive tachometer to each cylinder in turn and try to isolate the problem cylinder.
- Check trigger resistance and DVA output as shown below.
| Wire | Read To | Resistance | DVA |
|---|---|---|---|
| Brown wire (#1) | White wire (#2) | 800-1400 | 4V or more |
| Brown wire (#1) | Engine GND | Open | 1V or more (a) |
| White wire (#2) | Engine GND | Open | 1V or more (a) |
Note (a): This reading can be used to determine if a pack has a problem in the triggering circuit. If you have no fire on one cylinder and the trigger DVA reading for that cylinder is low, disconnect the trigger wire and recheck the DVA output to ground from that trigger wire. If the reading remains low, the trigger is bad.
- Check the DVA output on the green wires from the switch box while connected to the ignition coils. Check the reading on the switch box terminal and on the ignition coil terminal. You should read at least 150V or more at both places. If the reading is low on one cylinder, disconnect the green wire from that ignition coil and reconnect it to a load resistor, then retest. If the reading is now good, the ignition coil is likely bad. If it remains low, the power pack is likely bad.
Engine Will Not Rev Beyond 3000-4000 RPM
- Connect an inductive tachometer to each cylinder in turn and try to isolate the problem. A single cylinder dropping fire usually indicates the switch box or ignition coil. All cylinders acting up usually indicate a bad stator.
- Connect a DVA meter between the stator’s blue wire and blue/white wire and perform a running test. DVA voltage should jump to well over 200V and stabilize. A voltage drop right before the problem occurs indicates a bad stator. Use blue to engine ground if the engine has a red stator kit installed.
- Connect a DVA meter between the stator’s red wire and red/white wire. The DVA voltage should climb smoothly and remain high through the RPM range. A reading lower than what is seen on the blue wire indicates a bad stator.
High Speed Miss
- Connect an inductive tachometer to each cylinder in turn and try to isolate the problem. A large RPM variance on one cylinder usually points to the switch box or ignition coil. Occasionally the trigger can cause this same issue. Check the trigger as described above under “No Fire or Intermittent on One Cylinder.”
- Perform a high-speed shutdown and read the spark plugs. Check for water intrusion. A crack in the block can cause a high-speed miss when water pressure gets high, but a normal shutdown can mask the problem.
- Remove the flywheel and inspect the triggering and charge-coil magnets for cracks or broken magnets.