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1. 2.

Mercury

Two Cylinder Engines 1974-1985 (With the 339-5287 or 339-6222 Switch Box) NO SPARK ON ANY CYLINDER:

1. 2.

Disconnect the Orange stop wire and retest. If the ignition system now has spark, the stop circuit has a problem.

WIRE Orange

White

Read To Engine GND *

RESISTANCE 1600-1800 (800-900 per coil)

Brown

140-160

Check the stator and trigger resistance and DVA output:

DVA 180V or more 0.5V or more

Note: Some units had used a trigger that has 2 Brown wires instead of a Brown and White.

  • 3.

    Inspect the ignition coils. You should have either a red, orange or green coil with a bare braided ground wire coming out of the backside of the coil. This bare braided ground wire MUST be connected to a clean engine ground. You cannot use a black or blue ignition coil.

  • 4.

    Check the ignition coils as follows: Check resistance from + to – terminal reading should be 0.2-1.0 ohms and 800-1100 ohms from the high tension lead to engine ground. There should be no connection from the – terminal to engine ground.

  • 5.

    Check the flywheel for broken magnets.

ENGINE HAS SPARK BUT WILL NOT RUN: Index the flywheel and check the timing. If it is out by 180 degrees, swap the trigger wires to the switch box. If the timing is off by any other degree, check the flywheel key.

NO SPARK OR INTERMITTENT ON ONE CYLINDER:

  • 1.

    Check the DVA output between the Green wire and Green/Whites from the switch box, also between the Blue and Blue/White wires while they are connected to the ignition coils. You should have a reading of at least 150V or more. If the reading is low on one cylinder, disconnect the wires from the ignition coil for that cylinder and reconnect them to a load resistor. Retest. If the reading is now good, the ignition coil is likely bad. A continued low reading indicates a bad switch box.

  • 2.

    Connect an inductive tachometer to each cylinder and compare the RPM readings at the RPM where the problem is occurring. If only one cylinder is dropping out, swap the ignition coil locations and retest. If the problem follows a coil, replace the coil. If it stays on the same spark plug, replace the switch box.

  • 3.

    Check the flywheel magnets to see if one has come loose and moved.

Mercury

Two Cylinder Engines 1974-1985 (With the 332-4911 or 332-4733 Switch Box) NO SPARK ON ANY CYLINDER:

WIRE

Read To

RESISTANCE

Blue

Engine GND

3500-5500

Red

Engine GND

450-550

Brown

White*

140-160

1.

2.

Disconnect the Orange (or Black/Yellow) stop wire and retest. If the ignition system now has spark, the stop circuit has a problem. Check the stator and trigger resistance and DVA output:

CDI RESISTANCE

DVA 180V or more 20V or more 0.5V or more

3. Check the flywheel for broken magnets. ENGINE HAS SPARK BUT WILL NOT RUN:

  • 1.

    Index the flywheel and check the timing. If it is out by 180 degrees, swap the trigger wires to the switch box.

  • 2.

    If the timing is off by any other degree, check the flywheel key.

NO SPARK OR INTERMITTENT ON ONE CYLINDER:

  • 1.

    Check the DVA output from the switch box on the Green wires while they are connected to the ignition coils. You should have a reading of at least 150V or more. If the reading is low on one cylinder, disconnect the wires from the ignition coil for that cylinder and reconnect them to a load resistor. Retest. If the reading is now good, the ignition coil is likely bad. A continued low reading indicates a bad switch box.

  • 2.

    Connect an inductive tachometer to each cylinder and compare the RPM readings at the RPM where the problem is occurring. If only one cylinder is dropping out, swap the ignition coil locations and retest. If the problem follows a coil, replace the coil. If it stays on the same spark plug, replace the switch box.

  • 3.

    Check the flywheel magnets to see if one has come loose and moved.

48

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