8 Common Signs & Symptoms of a Bad Outboard Ignition Coil

An outboard ignition coil is an important part of an outboard engine. The coil transforms potential energy (voltage) from battery to spark the plugs. Which causes ignition.

When an outboard coil goes bad, the engine cannot jump to start. Because the coil cannot convert the energy required to create spark and ignite the engine.

What Are the Symptoms of a Bad Outboard Ignition Coil?

The symptoms of a bad outboard coil are as follows:

1. The Engine Doesn’t Start

This is the most obvious symptom. Engine ignition requires a spark in the plug gap. The spark plugs.

A fouled spark plug, that is a plug covered in oil, carbon or other stuff causes a weak spark. A damaged or weakened coil produces weak spark as well.

A weak spark cannot cause ignition. Ignition is necessary for jump-starting the engine by breaking the resting inertia.

As the potential energy of the battery cannot be converted by a weaker coil into ignition energy, the engine fails to start.

2. Misfiring Engine

The engine runs oddly or uncontrollably when it is started. In this case, the coil has enough juice to start the engine. But not enough to keep running smoothly.

This change is noticed in the acceleration of the engine as well. There is no uniform acceleration, the boat runs either too fast or too slow. And these two states keep switching in between.

The same thing is indicated when you start the boat, but it stops as soon as you give it throttle.

These unpredictable changes might seem like it’s an electrical issue. If so, then chances are it might be a bad coil.

3. Resistance Test Results

The positive and negative terminal wires of the primary circuit and the spark plug from the coil tower should be disconnected first.

On the voltmeter, the dial should be turned to OHMS. For an outboard motor, set the range to 200.

Placing one of its probes on the positive terminal of a primary circuit, measure the resistance. If the value in the case of the primary circuit does not fall between 0.2 to 0.4 OHMS, your coil is bad.

Similarly measure the resistance of the secondary circuit, this time touching the negative terminal with the probe. If the range does not lie between 8 to 11 OHMS, you have a bad coil.

4. Cracks and Breakages in the Coil

You can check the coil by opening up the outboard motor. A bad coil will definitely have some physical damage to it. That includes the coil being broken or cracked.

In the cap and rotor, there might be corrosion too.

5. Engine Stops When Warm

The coil goes out when the engine is warm due to thermal expansion. It is rather hard to detect the bad coil based on this symptom alone. Because most ignition related issues display this symptom.

6. Spark Test

This is a very easy test you can conduct with a simple timing light. The timing light does not produce a spark or produces a weak spark in addition to the spark plug.

7. Plug Health

Keeping your boat unused for a longer period of time can cause bad plug health. This includes corrosion of spark plug, even fouling.

Moreover, the gas if not emptied, turns into a black muck-like substance. This is bad for the ignition of the engine.

Check if your spark plugs are alright. If they are not and you still continue to use it, this will put load on your coil. So even if you replace or fix the plugs, your engine may not start because the coil has already gone bad.

8. Sparks Firing at the Wrong Cylinder

If the engine is a multi-cylinder one, you may notice that sparking occurs at the wrong cylinder at the wrong time.

Erratic sparking may occur in the cylinders at the wrong time as well.

How Should You React If You Detect a Outboard Ignition Coil Bad?

You will naturally be looking to replace the coils. In this case, you can buy a coil online. The cost will depend on the type of engine you have. This is the most primary and cost-friendly thing you can do.

You can also repair an ignition coil. It is comparatively cheaper to fix.

Before you fix or replace the coil, stop using the engine. It might cause harm to other parts of the engine. It will also add load to the already damaged coil.

Is Replacing a Bad Outboard Coil Typically Expensive?

Outboard coils are pretty inexpensive. You can buy one from Amazon, AliExpress, eBay, or any store selling spare parts. They cost only a couple of bucks. A range would be from $18-100 online.

However, repairing costs of an ignition coil ranges from $200-400. This is a little high and the service charge consists of more than 50%.

You can save about $120-130 dollars if you replace an ignition coil yourself. The sum total cost of parts you need to replace the entire coil would be around $165-250.

How Often Should You Inspect or Service the Outboard Coil?

If you don’t do boating often, keep the coil in check at least every 3 months. If you do it frequently and load your coil, the interval should be lesser.

Service the outboard coil only when it is broken or damaged. However, keep the plugs clean. Make sure there is no fouling of the plugs.

For the health of the coil, do not load the coil. Moreover, excess heat, vibration can damage the coil easily.

Final Thoughts

Premature failure of the overboard coil can be a financial hindrance to boat owners.

Learning about coil health is therefore important. Firsthand knowledge about machinery, e.g. changing or replacing coils is necessary.

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