Unveiled: The Ultimate Guide to Testing Ignition Coils on Johnson Outboards

An ignition coil plays a crucial role in the smooth operation of your Johnson outboard motor. Its primary function is to generate a high-voltage spark that ignites the air-fuel mixture in the engine’s cylinders. A faulty ignition coil can lead to engine misfires, rough idling, and reduced power. Therefore, it’s essential to know how to test an ignition coil on a Johnson outboard to ensure optimal performance and prevent costly repairs.

Step 1: Safety First

Before you begin testing the ignition coil, ensure your safety by disconnecting the negative terminal from the battery. This will prevent any accidental electrical shocks.

Step 2: Identify the Ignition Coil

Locate the ignition coil on your Johnson outboard. It’s typically mounted on the engine’s powerhead and has two terminals: a primary terminal connected to the ignition switch and a secondary terminal connected to the spark plug wires.

Step 3: Visual Inspection

Start by visually inspecting the ignition coil for any signs of damage or wear. Look for cracks, burns, or loose connections. If you notice any abnormalities, it’s best to replace the ignition coil immediately.

Step 4: Resistance Measurement

Using a multimeter set to the ohms scale, measure the resistance between the primary terminals of the ignition coil. The normal resistance value for a Johnson outboard ignition coil typically ranges from 0.5 to 2 ohms. If the measured resistance falls outside this range, the ignition coil may be faulty.

Step 5: Secondary Resistance Measurement

Next, measure the resistance between the secondary terminal of the ignition coil and the spark plug wire terminal. The normal resistance value for this test varies depending on the outboard model and should be in the range of 5,000 to 15,000 ohms. If the measured resistance is significantly higher or lower than the specified range, the ignition coil may be faulty.

Step 6: Spark Test

The spark test is a crucial step in testing the ignition coil. Connect a spark plug to the secondary terminal of the ignition coil and hold it close to the engine block. Start the engine and observe the spark. A strong, consistent spark indicates a healthy ignition coil. If the spark is weak or intermittent, the ignition coil may be faulty.

Step 7: Output Voltage Test

Using a voltmeter, measure the output voltage of the ignition coil. Set the voltmeter to the AC voltage scale and connect the probes to the primary and secondary terminals of the ignition coil. Start the engine and observe the voltage reading. The normal output voltage for a Johnson outboard ignition coil typically ranges from 20,000 to 40,000 volts. If the measured voltage is significantly lower or higher than this range, the ignition coil may be faulty.

Recommendations

Testing an ignition coil on a Johnson outboard is a straightforward process that can help you diagnose ignition issues and ensure your engine runs smoothly. By following the steps outlined in this guide, you can accurately determine the condition of your ignition coil and make informed decisions regarding repairs or replacements.

Answers to Your Questions

Q: How often should I test my Johnson outboard ignition coil?
A: It’s recommended to test your ignition coil every 50 to 100 hours of operation or annually, whichever comes first.

Q: Can I replace the ignition coil on a Johnson outboard myself?
A: Yes, replacing the ignition coil is a relatively straightforward task that can be performed with basic tools. However, it’s important to follow the manufacturer’s instructions carefully to avoid any damage to the engine.

Q: What are the symptoms of a faulty ignition coil on a Johnson outboard?
A: Symptoms of a faulty ignition coil include engine misfires, rough idling, reduced power, and difficulty starting the engine.