Mercury Outboard Engine Ignition Components

Mercury Marine Motor Ignition Components Resources and Information

Every electric start Mercury outboard has an ignition switch that opens and shuts the starter solenoid. Marine ignition is designed for performance marine applications where a high energy and reliable ignition is a necessity. PartsVu is happy to offer a wide selection of quality certified Mercury outboard motor ignition parts to fit your outboard engine’s exact specifications. 

We also regularly publish helpful resources to help you maintain your Mercury outboard motor, such as:

• Mercury Outboard 100-hour Service Guides
• Mercury Outboard Service Schedule
• Mercury Outboard Serial Number Lookup

Mercury Outboard Engine Ignition Components FAQs

How do I start my Mercury outboard engine? 

Mercury makes a 2-stroke and 4-stroke engine. The 4-stroke engines have risen in popularity due to their reduced noise, fuel efficiency, and greater longevity. Because they’ve grown in popularity in recent years, most of them tend to be newer. Typically, they’re as easy to start as tilting them down and turning the key. 

In contrast, a carbureted 2-stroke may not be as simple to start.

1. First, tilt the engine so that the fuel can more easily reach the carburetor
2. Prime the bulb until it’s too hard to squeeze
3. While in neutral, advance the throttle to ⅔
4. Turn the key, push to choke and crank
5. Release the choke and return to neutral

How do I start a flooded Mercury outboard motor?

What causes a flooded Mercury outboard motor, and what does it mean? A flooded motor has too much fuel in the cylinder, and it can therefore be very difficult– or impossible– to start. A strong smell of gasoline may indicate that this has occurred. 

Even if your motor does start while flooded, it’s important to address it immediately anyway. Running a flooded motor can damage the whole system, leading to a much larger (and more expensive) set of problems. 

Now, to address the problem: wait about five minutes before you clear-flood start the engine. You do this by moving the throttle to the clear-throttle or wide-open throttle position and crank your engine. This allows air to enter the engine, but not fuel, and should get things moving along. It may take a few tries for this to be effective.

How do I manually start an electric start outboard engine? 

If the engine is under 25HP, you shouldn’t have too much trouble removing the cowl cover and using the emergency cord to pull-start. This is generally possible for engines up to 50HP, but it will be increasingly difficult the higher the horsepower. To do this:

1. Ensure that the key is in the on position and that the shift is in neutral 
2. If you’re using a rope, tie a knot so that the rope can be secured in the notch in the flywheel
3. Wrap the rope around the flywheel in the correct direction for your engine, which is most likely clockwise
4. Pull repeatedly until the engine starts
5. Put the cowling back on once the flywheel stops spinning

If this doesn’t solve your problem, you may need to go through a more thorough troubleshooting process. Our guide, Why Your Mercury Outboard Motor Stopped Working, outlines everything you’ll need to check in greater detail, with handy flowcharts for reference.

Why did my Mercury outboard motor stop working?

Your Mercury outboard ignition system is responsible for firing up the engine and keeping it running. Because checking this system may involve sparks and heat, keep flammable liquids away. 

The first part of the ignition system to check is the spark plugs. Clean and adjust the spark plugs– they may need to be replaced. Learn what to look for and how to perform spark plug replacement with our comprehensive guide.

Check the ignition spark with a spark gap tester. If you’ve got a good spark, make sure that the air gap is within specification. Adjust it if needed. If you have a good spark and the gap is within specification, the problem will likely not be found in the ignition system.

However, if you don’t have a good spark, salt buildup on the spark plug caps or ignition coil leads could be causing problems. You’ll also need to check both the spark plug caps and ignition coil leads for proper resistance. Replace degraded parts. When there is no salt buildup and both parts have proper resistance, check the ECM output peak voltage.

If your spark plugs don’t seem to be the issue, check that the electric oil pump and oil level sensor are in good condition. If so, check the reed valve for its condition.

How do I change my Mercury 4-stroke outboard spark plugs?

For most applications, the spark plugs come pre-gapped, but it is advisable to re-check gap to make sure that plugs were not damaged during manufacturing or shipment.

While removing the old spark plugs, keep track of which plugs come from which cylinders.

• Note if the plug appears to be wet from water, oil, or gasoline.
•  Note if the plug exhibits evidence of heavy carbon deposits or other fowling as well as any rust – all indicative of problems.

If you were to take your engine to a dealer for your 100-hour service, they would perform a compression test by connecting a compression gauge to the individual cylinders and using the starter motor to turn over the engine. By measuring the engine’s ability to pressurize the cylinder, you can glean information about the condition of the engine internals. To perform this test at home, you will either need a remote starter button, or a friend who can turn the ignition key with the kill lanyard removed.

This cranking with the ignition disabled will also prime the fresh oil around the block, reducing friction at startup after the service. Repeat testing for all cylinders and compare results. Readings will vary from gauge to gauge, so the test is more about measuring the difference in readings with ideal results being less than 10 percent variance.

After the compression test is completed – or skipped – you can now begin installing your new spark plugs. For ease of future removal and to reduce the risk of thread damage to the cylinder head, apply a tiny amount of anti-seize compound to the threads of the plug. Use care to avoid contacting the electrode or porcelain center of the plug. Thread the plugs into the cylinder head by hand using caution not to cross thread.

Most modern spark plugs use a crush washer that will press down and provide a tight seal as you tighten. Full torque is between 18-21 ft. lbs. Reinstall the plug wires or coils in the same order they came off. Mercury’s service manual recommends using Loctite 271 (Red High Strength) on the bolts that hold the pencil coils over the spark plug, but we find Loctite 242 (Blue Removable Strength) might be a better choice.

How do I change my Mercury 2-stroke outboard spark plugs?

While removing the old spark plugs, keep track of which plugs come from which cylinders.

•  Note if the plug appears to be wet from water, oil, or gasoline.
•  Note if the plug exhibits evidence of heavy carbon deposits or other fowling as well as any rust – all indicative of problems.

If you were to take your engine to a dealer for your 100-hour service, they would likely perform a compression test by connecting a compression gauge to the individual cylinders and using the starter motor to turn over the engine. By measuring the engine’s ability to pressurize the cylinder, you can glean information about the condition of the engine internals. To perform this test at home, you will either need a remote starter button, or a friend who can turn the ignition key with the kill lanyard removed.

This cranking with the ignition disabled will also prime the fresh oil around the block, reducing friction at startup after the service. Repeat testing for all cylinders and compare results. Readings will vary from gauge to gauge, so the test is more about measuring the difference in readings with ideal results being less than 10 percent variance.

After the compression test is completed – or skipped – you can now proceed with your Mercury 2-stroke spark plugs and compression service by installing your new spark plugs. For ease of future removal and to reduce the risk of thread damage to the cylinder head, apply a tiny amount of anti-seize compound to the threads of the plug. Use care to avoid contacting the electrode or porcelain center of the plug. Thread the plugs into the cylinder head by hand using caution not to cross thread.

Most modern spark plugs use a crush washer that will press down and provide a tight seal as you tighten. Full torque is between 18-21 ft. lbs. Reinstall the plug wires or coils in the same order they came off.

Will a corroded ignition coil for Mercury outboard engines still work?

A corroded ignition coil for a Mercury outboard engine may still work to some extent, but it is not recommended to continue using a corroded coil as it can lead to further problems and engine damage.

Corrosion on the ignition coil can cause electrical resistance that can interfere with the flow of current and weaken the spark that is needed to ignite the fuel in the engine. Over time, the corrosion can worsen and lead to a complete failure of the ignition coil.

If you suspect that the ignition coil on your Mercury outboard engine is corroded, it's best to have it inspected and tested by a qualified technician. In most cases, a corroded ignition coil will need to be replaced in order to ensure proper engine performance and reliability.

What are the most common Mercury outboard ignition problems?

There are several common ignition problems that can occur with Mercury outboard motors. Here are a few examples:

1. Faulty spark plugs: If the spark plugs are worn or fouled, it can cause the engine to misfire or fail to start.
2. Bad ignition coils: Ignition coils are responsible for providing the electrical charge that is needed to ignite the fuel in the engine. If a coil fails, the engine may misfire or fail to start.
3. Failed stator or trigger: The stator and trigger are part of the engine's ignition system and are responsible for generating the electrical charge that is needed to power the ignition coils. If these components fail, the engine may not start or may run poorly.
4. Wiring issues: Problems with the wiring or connections in the ignition system can also cause issues with starting or running the engine.
5. Failed ignition switch: If the ignition switch fails, it can prevent the engine from starting or cause it to shut off unexpectedly.
6. Fuel system issues: Problems with the fuel system, such as a clogged fuel filter or faulty fuel pump, can also cause ignition problems by preventing the engine from getting enough fuel.

Which Mercury outboard parts do I need to replace my ignition?

The specific parts you will need to replace the ignition on your Mercury outboard will depend on the make and model of your engine. However, some common parts that may need to be replaced include the ignition switch, ignition coil, spark plugs, and spark plug wires.

To ensure that you have all the necessary parts, it's recommended that you consult your engine's manual or contact a certified Mercury technician for guidance on the exact parts you will need. They will be able to provide you with specific recommendations and help ensure that your ignition replacement is performed safely and correctly.

How to wire a Mercury outboard ignition switch?

Wiring a Mercury outboard ignition switch can vary depending on the specific model and year of the motor, as well as the type of ignition switch being used. Generally, it's recommended to follow the wiring diagram included with the ignition switch to ensure proper installation. However, if you're unsure about how to wire the switch or if you're not comfortable working with electrical components, it's always best to consult a qualified marine technician or dealer for assistance.

What safety precautions should I follow for Mercury outboard ignition wiring?

When working with Mercury outboard ignition wiring, it's important to follow proper safety precautions to prevent electrical shock and other hazards. Here are some general guidelines to follow:

1. Disconnect the battery: Before beginning any work on your outboard's ignition system, always disconnect the battery to prevent electrical shock and damage to your engine.
2. Wear protective gear: Wear protective gear, such as rubber gloves and safety glasses, to protect yourself from any potential electrical hazards or debris.
3. Work in a dry area: When working with ignition wiring, make sure to do so in a dry, well-ventilated area to minimize the risk of electrical shock or other hazards.
4. Follow the wiring diagram: Refer to your engine's wiring diagram to ensure that you are correctly identifying and connecting the wires.
5. Inspect wiring for damage: Before making any changes or connections to the ignition system, inspect the wiring for any signs of damage or wear. Replace any damaged wires or connectors before proceeding.
6. Follow manufacturer guidelines: Always follow the manufacturer's guidelines and instructions when installing or replacing any ignition components.
7. Test the ignition: Once you have completed the installation, test the ignition to ensure that it is working properly before operating your outboard.

By following these safety precautions, you can help ensure that your ignition replacement is performed safely and effectively. If you have any doubts about your ability to perform the work, it is recommended that you consult a certified Mercury technician.

How to replace Mercury outboard ignition switch?

To replace the ignition switch on a Mercury outboard motor, you'll typically need to remove the old switch from the dash or console, disconnect the wiring harness, and install the new switch in its place. Again, the exact steps can vary depending on the specific motor and switch, so it's always best to consult the manufacturer's instructions or a qualified marine technician for guidance.

How to troubleshoot Mercury outboard ignition?

If you're experiencing issues with your Mercury outboard ignition system, there are several steps you can take to troubleshoot the problem. First, check the battery to make sure it's fully charged and in good condition. Next, check the spark plugs and ignition coils to make sure they're functioning properly. You may also want to check the wiring and connections to ensure they're secure and free of damage or corrosion. If you're unable to identify the problem or if the issue persists, it's best to consult a qualified marine technician or dealer for further diagnosis and repair.

How long does a Mercury outboard ignition switch last?

The lifespan of a Mercury outboard ignition switch can vary depending on several factors, such as the quality of the switch, how often it's used, and the environmental conditions in which it's used.

In general, an ignition switch on a Mercury outboard can last for several years with proper use and maintenance. However, if the switch is exposed to harsh conditions such as saltwater, extreme temperatures, or heavy usage, it may wear out more quickly and require replacement sooner.

It's important to keep an eye out for signs of wear or damage to the ignition switch, such as difficulty turning the key or a loose connection, and replace it promptly if necessary. Routine maintenance and inspection can also help prolong the lifespan of the switch and ensure reliable operation of the outboard motor.

Can a Mercury outboard ignition coil replacement be performed by most amateur boaters?

Replacing a Mercury outboard ignition coil may be possible for some amateur boaters, but it depends on their level of experience and comfort with mechanical work.

If you are familiar with basic engine maintenance and have the necessary tools, replacing an ignition coil on a Mercury outboard may be a straightforward task. However, if you are inexperienced with engine work or unsure about how to proceed, it's best to consult a professional mechanic or technician.

Improper installation of an ignition coil can cause further damage to the outboard motor, and may lead to more costly repairs down the line. It's important to take the necessary precautions and ensure that the replacement is done correctly to avoid any potential issues.

What is a Mercury outboard thunderbolt ignition?

The Mercury Thunderbolt ignition is a type of ignition system used on some older Mercury outboard motors. It was first introduced in the 1960s and was used on various Mercury outboard models until it was eventually replaced by newer ignition systems.

The Thunderbolt ignition system uses a set of contact points to create a spark that ignites the fuel in the engine. The system also includes a capacitor that stores electrical energy and helps to ensure a strong spark. The Thunderbolt ignition was known for its reliability and performance, and was a popular choice among boaters in its time.

While the Thunderbolt ignition system is no longer used in new Mercury outboard motors, it is still found on some older models that are still in use today. If you have an older Mercury outboard with a Thunderbolt ignition, it's important to keep up with regular maintenance and inspections to ensure that the ignition system is functioning properly.

What should I do if I lose my Mercury outboard motor ignition key?

If you lose your Mercury outboard motor ignition key, there are a few steps you can take to get a replacement key:

1. Contact a Mercury dealer: The best and easiest way to get a replacement key is to contact your nearest Mercury dealer. They will ask you for your engine serial number and can cut a new key for you.
2. Call a locksmith: A locksmith may also be able to make a replacement key for your Mercury outboard motor. However, they may need to visit your boat to make the key, which can be inconvenient.
3. Order online: There are some online retailers that sell Mercury outboard motor ignition keys. However, you will need to provide them with your engine serial number and wait for the key to be shipped to you.

Regardless of which option you choose, it is important to have a spare key made so that you do not get stranded on the water in case you lose your key again.

What provides ignition in each engine cylinder?

In most outboard engines, ignition in each engine cylinder is provided by a spark plug that ignites the fuel mixture inside the cylinder. The ignition system generates a high voltage electrical charge that travels through the spark plug wire to the spark plug, creating a spark that ignites the fuel and air mixture.

How do you test an outboard ignition module?

Testing an outboard ignition module requires specialized tools and knowledge. A common test is to use a digital multimeter to check the resistance of the ignition coil, which should be within the manufacturer's specified range. Another test involves checking the output voltage of the module while the engine is cranking. If you suspect a problem with your outboard ignition module, it's best to consult a professional mechanic or technician to diagnose and repair the issue.

What are the symptoms of a bad trigger on an outboard?

A bad trigger on an outboard can cause a variety of symptoms, including difficulty starting the engine, intermittent stalling, and loss of power. The engine may also run poorly or misfire, and the tachometer may not function correctly. If you suspect a problem with the trigger on your outboard, it's important to have it inspected and repaired as soon as possible to avoid further damage to the engine.

How does a marine ignition switch work?

A marine ignition switch is used to turn the engine on and off, and to control the electrical power to various components on the boat. The switch works by completing or interrupting the electrical circuit that runs from the battery to the ignition system and other electrical components. When the switch is turned to the "on" position, it completes the circuit and allows electricity to flow, powering the engine and other systems on the boat. When the switch is turned to the "off" position, it interrupts the circuit and cuts off the flow of electricity, shutting down the engine and other systems.

What are the most common Mercury outboard ignition switch problems?

The most common problems with Mercury outboard ignition switches are:

1. Electrical issues: Faulty wiring, a corroded or loose connection, or a blown fuse can prevent the switch from functioning properly.
2. Ignition switch failure: Over time, the ignition switch can wear out or become damaged, preventing it from turning or working properly.
3. Key problems: Worn, damaged or lost keys can cause issues with the ignition switch.
4. Ignition module failure: The ignition module controls the spark plug firing in the cylinders, and if it fails, the engine will not start or run properly.
5. Safety switch failure: The safety switch is a critical component that prevents the engine from starting if it is not in the neutral position or if the boat is not in the water. If the safety switch fails, the engine may not start or may shut off while underway.

If you are experiencing issues with your Mercury outboard ignition switch, it is important to have it inspected by a qualified technician to determine the root cause of the problem and to ensure that your boat is safe to operate.

Is it smart to buy a used Mercury outboard ignition coils for sale?

It is generally not recommended to buy used ignition coils for your Mercury outboard motor. Ignition coils are critical components of your engine's ignition system, and they are subject to wear and tear over time. Used coils may be damaged or have lower performance than new ones, and they may fail prematurely, leading to engine misfires or even engine damage.

Furthermore, it can be difficult to determine the condition of a used ignition coil, as it may appear to be in good working order but may fail soon after installation. It is usually best to purchase new, high-quality ignition coils from a trusted supplier to ensure the safety and reliability of your Mercury outboard motor.

What's the difference between a Mercury outboard 10 wire ignition switch and a Mercury outboard 6 wire ignition switch?

The primary difference between a Mercury outboard 10-wire ignition switch and a Mercury outboard 6-wire ignition switch is the number of wires used in the switch.

The 10-wire ignition switch is typically used on larger Mercury outboard engines, and it features additional wires that control various functions such as the choke, tilt and trim, and accessory power. This switch is more complex and requires a more sophisticated wiring harness to connect to the engine.

The 6-wire ignition switch is typically used on smaller Mercury outboard eng