Mercury Outboard Bad Coil Symptoms

Mercury Marine manufactures Mercury Outboards. Mercury Marine has been building boats since 1892. The company was founded by Charles E. Sperry, who wanted to make a boat faster than other boats at its time.

Mercury Outboards are known for being durable and reliable. However, sometimes these engines fail to perform correctly. Sometimes, the problem may lie in the motor itself. If there’s no power at all, then check the wiring or electrical components first.

Mercury outboard motors are among the most reliable engines around. They were costly too. If you’ve ever had a problem with your Mercury motor, then you probably know that it might be tough to be fixed.

If you have a Mercury outboard with a bad coil, you may experience several symptoms, including difficulty starting, poor performance, and engine noise. 

Arrange your outboard servicing right away if you notice any of these lousy motor symptoms. 

Mercury outboard bad coil symptoms

If your Mercury outboard isn’t starting, has low power, or is running rough, it may have a bad coil. Symptoms of a bad coil include hard starting, low energy, and running rough. 

Mercury outboard bad coil symptoms include:

The engine will not start:

The first symptom of a bad mercury outboard motor coil is that the engine will not start. Several different things can cause this, but in most cases, it’s because the ignition switch has been turned off or the key removed from the ignition. If you have an older model outboard motor with a mechanical igniter, this could also cause problems.

Mercury Outboard Bad Coil Symptoms
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Clicking Sound: 

The following symptom is that the engine may run for a few seconds and then stop. If you hear any clicking sounds when you turn on the ignition, this indicates that there is no spark to ignite the fuel mixture. It might also suggest that the spark plug wires are disconnected.

High voltage:

The third symptom is that the engine won’t even cry before trying to start the engine again. If you notice the voltage is too low, replace the battery. If the voltage is high, disconnect the battery’s negative terminal from the starter solenoid and try cranking the engine again.


The most common symptom of a bad mercury outboard motor coil is the smell, which may be noticeable when you start your engine. A bad mercury outboard motor can also cause other problems, including overheating and burning up the motor. If any signs or symptoms appear with your motor, it’s time to get your boat repaired.

How Do You Test a Coil on a Boat Motor?

If you have been having trouble starting your engine, then you probably know what a bad ignition coil looks like. A bad coil can cause your engine not to start. When the coil fails, it prevents the spark from reaching the cylinder.

You need to remove the spark plugs wire before testing a coil. Then, it would help if you disconnected the battery cables. Next, you need to turn the key in the “on” position. After doing so, you should wait several seconds before turning the key back off. If the engine starts right away, then the coil is working fine.

However, if it takes more than 10 seconds to start up, there could be a problem with the coil.

What Causes Bad Coils?

There are many reasons why a coil may malfunction. Corrosion is one of the most common causes. This occurs because water gets inside the coils. When this happens, the wires inside the coil become brittle. This makes the cables less conductive. As a result, the coil does not work as well.

Another reason coil malfunction can happen is improper maintenance. For example, if you don’t change a car’s regular oil, then it can become dirty. Dirty oil reduces the lifespan of the coil. Also, if you neglect to clean the air filter, then dirt can build up inside the system.

A third possible cause of a bad coil is a loose connection. If one of the connections becomes loose, the coil may not function correctly.

How To Fix A Mercury Outboard Motor?

  • The first step in fixing a bad mercury outboard is turning off the motor’s power. It would help if you never attempted to repair a lousy mercury outboard while it’s running. 
  • Once the power has been shut off, disconnect the battery cables from the terminals on the side of the battery. 
  • Then remove the negative terminal cover and pull out the wires that connect to the negative terminal. This will allow you to the positive terminal.
  • Next, unscrew the two screws holding down the top of the motor. Lift the top of the motor off. Remove the old coil by pulling it straight out of the bottom of the engine. Be careful not to break the connections between the coils and the stator.
  • Replace the new coil with the one provided with the replacement part. Install the new coil into the motor by pushing it until it snaps into position. 
  • Reattach the top of the motor and replace the screws. Reconnect the battery cables to the terminals on the side. Turn the ignition key on again and test. 

Frequently Asked Questions: 

Question: How Often Should You Inspect the Mercury Outboard Coil?

Answer: Mercury Boaters should service their engines regularly. Keep the engine cool by keeping the water temperature low. Do not overload the engine. Clean the plugs regularly. Avoid loading the machine if it is broken or damaged, as this could cause excessive heat and possible damage to the engine.

Question: Can a bad ignition coil cause a car to vibrate?

Answer: If you stop the car suddenly, a misfiring from an old ignition coil could cause your vehicle to run rough. This might also vibrate or shake when you try starting it again. Your car’s engine needs a spark when it needs one.

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Wrap up: 

Mercury Marine manufactures Mercury Outboards. They are designed to provide reliable performance. When your Mercury outboard motor isn’t running right, it can be hard to determine the root of the problem. One common issue that can cause various symptoms is a bad coil. If you’re experiencing one of the mentioned problems, it might be time to check your coil. There are several ways of fixing a bad Mercury outboard motor. One way is to replace the entire engine. Another way is to replace only the wrong part. For the best suitable solution for your mercury outboard coil, contact professionals. 

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