Unlock the Secrets: How to Test Johnson Outboard Ignition Coil

The heart of your Johnson outboard‘s ignition system is the ignition coil. This crucial component transforms the low voltage from your battery into a high-voltage spark that ignites the fuel-air mixture, propelling your boat forward. When your Johnson outboard sputters, coughs, or refuses to start, a faulty ignition coil is often the culprit. Knowing how to test your Johnson outboard ignition coil can save you time, money, and frustration.

Understanding the Ignition Coil’s Role

The ignition coil acts as a transformer, stepping up the low voltage from your battery to a high voltage required to create a spark. This spark is delivered to the spark plugs, igniting the fuel-air mixture in the combustion chamber. A healthy ignition coil provides a consistent, powerful spark, ensuring smooth and reliable engine operation.

Recognizing the Signs of a Faulty Ignition Coil

Before diving into testing, it’s important to recognize the common symptoms of a failing ignition coil. These include:

• Difficulty Starting: A faulty ignition coil might struggle to create enough spark to ignite the fuel, resulting in a hard-to-start engine.
• Misfiring: Irregular or weak sparks can lead to misfiring, causing the engine to run rough, sputter, or lose power.
• No Spark: In severe cases, a completely dead ignition coil will result in no spark at all, leaving your engine unable to start.
• Engine Stalling: A weak spark can cause the engine to stall, particularly under load or at higher RPMs.

Essential Tools for Testing Your Ignition Coil

Before you begin testing, gather the necessary tools. You’ll need:

• Multimeter: A multimeter is essential for measuring voltage, resistance, and continuity.
• Spark Plug Wrench: This is used to remove and install the spark plugs.
• Spark Plug Tester: This device allows you to visually inspect the spark generated by the ignition coil.
• Safety Glasses: Always wear safety glasses to protect your eyes from potential debris or sparks.

Testing the Ignition Coil: A Step-by-Step Guide

Now, let’s walk through the steps to test your Johnson outboard ignition coil:

1. Disconnect the Battery: For safety, always disconnect the negative terminal of your battery before working on the ignition system.
2. Locate the Ignition Coil: The ignition coil is typically located near the engine’s cylinder head. It’s usually a cylindrical or rectangular component with electrical wires connected to it.
3. Check for Visual Damage: Inspect the ignition coil for any signs of physical damage, such as cracks, burns, or loose connections.
4. Test the Primary Winding Resistance: Using your multimeter, set it to the ohms (Ω) setting. Connect the positive lead of the multimeter to the primary terminal of the ignition coil, and the negative lead to the negative terminal. Consult your Johnson outboard service manual for the specified resistance range for your specific model.
5. Test the Secondary Winding Resistance: Repeat the resistance test for the secondary winding. The secondary terminal is usually marked with a higher voltage rating. Again, refer to your service manual for the appropriate resistance range.
6. Test for Continuity: Set your multimeter to the continuity setting. Connect the positive lead to the primary terminal and the negative lead to the secondary terminal. A healthy ignition coil should show continuity between these terminals.
7. Test for Spark: If the primary and secondary resistance readings are within the specified range, remove a spark plug and connect the spark plug tester to it. Connect the other end of the tester to the ignition coil’s secondary terminal. With the engine turned off, crank the engine briefly. A bright blue spark should jump across the gap in the spark plug tester.

Interpreting the Test Results

• Resistance Readings: If the resistance readings are outside the specified range, it indicates a problem with the coil’s windings.
• Continuity Test: A lack of continuity between the primary and secondary terminals points to a broken internal connection.
• Spark Test: A weak or absent spark confirms a faulty ignition coil.

Replacing a Faulty Ignition Coil

If your tests reveal a faulty ignition coil, it’s time to replace it. Here’s what you need to do:

1. Disconnect the Battery: Always disconnect the battery before replacing any electrical components.
2. Remove the Faulty Coil: Unplug the electrical connectors from the ignition coil and remove any mounting bolts or clamps holding it in place.
3. Install the New Coil: Carefully install the new ignition coil, ensuring that the electrical connectors are properly plugged in and that the coil is securely mounted.
4. Reconnect the Battery: Once the new coil is installed, reconnect the battery.

Troubleshooting Tips

• Check Spark Plugs: While testing the ignition coil, examine the condition of your spark plugs. Worn, fouled, or damaged spark plugs can hinder the ignition process.
• Inspect Wiring: Inspect the wiring leading to and from the ignition coil for any signs of damage, corrosion, or loose connections.
• Clean Electrical Connections: Clean any corroded or dirty electrical connections with a wire brush or contact cleaner.

Navigating the Waters of Success: A Recap

By mastering the art of testing your Johnson outboard ignition coil, you’ll be empowered to diagnose and address ignition issues quickly and efficiently. Remember to always prioritize safety by disconnecting the battery before working on any electrical components. With a bit of patience and attention to detail, you can keep your Johnson outboard running smoothly and enjoy countless hours on the water.

Frequently Asked Questions

1. Can I test an ignition coil without removing it?

While some tests can be performed with the coil in place, it’s generally recommended to remove it for a more thorough inspection and testing. This allows for easier access to the terminals and ensures accurate readings.

2. What are the common causes of a faulty ignition coil?

Common causes include:

• Heat Damage: Excessive heat can degrade the coil’s insulation, leading to short circuits or open circuits.
• Vibration: Constant vibration from the engine can stress the coil’s internal components, causing them to fail.
• Moisture: Exposure to moisture can cause corrosion and damage to the coil’s electrical connections.
• Age: Over time, the insulation material in the coil can deteriorate, leading to reduced performance.

3. How can I prevent ignition coil failure?

• Regular Maintenance: Follow the recommended maintenance schedule for your Johnson outboard, including regular inspections of the ignition system.
• Proper Cooling: Ensure that the engine is properly cooled to prevent overheating of the ignition coil.
• Avoid Excessive Vibration: Minimize exposure to excessive vibration by maintaining proper engine mounts and avoiding harsh operating conditions.
• Storage: Store your outboard properly to protect it from moisture and extreme temperatures.

4. Can I use a universal ignition coil on my Johnson outboard?

While some universal ignition coils may be compatible with certain Johnson outboard models, it’s always best to consult your service manual or a qualified technician to ensure compatibility. Using the wrong coil can lead to performance issues or damage to your engine.

5. What is the average lifespan of an ignition coil?

The lifespan of an ignition coil can vary depending on factors such as usage, maintenance, and operating conditions. However, a well-maintained ignition coil can typically last for several years. If you notice any signs of failure, it’s best to replace it promptly to avoid potential engine problems.