Mercury Mercruiser Ignition

Mercury MerCruiser Ignition Components Resources and Information

PartsVu is happy to stock a wide selection of certified Mercury MerCruiser electrical ignition components to fit the exact specifications of your engine. Whether you’re looking for MerCruiser Distributor Caps, Mercury MerCruiser Distributor Cap and Rotor Kits, and more, we have what you need to make sure your MerCruiser starts up like new every time.

For more information on MerCruiser ignition parts and how to perform DIY repairs for your entire engine, check out some of our helpful MerCruiser resources:

• MerCruiser Inboard Maintenance
• MerCruiser Maintenance Parts Library
• Mercury Outboard and Mercruiser Resources Collection

MerCruiser Electrical Ignition FAQs

How do I start my Mercury MerCruiser engine? 

In most cases, starting your Mercury Mercruiser motor only requires tilting the engine and turning the key. 

If this isn’t the case, you may need to troubleshoot which systems aren’t operating as required for a clean start before replacing your MerCruiser ignition control module. Here’s a few suggestions on where to start:

1. Tilt the engine so that the fuel can more easily reach the carburetor (if your MerCruiser is equipped with fuel injection, tilting isn’t required but may help offset any other issues). 
2. Squeeze the primer bulb a few times to enable fuel to circulate. Obstruction and contaminated fuel may impede the flow of gas from the fuel tank to the rest of the system.
3. Check the battery connection and voltage level. Consider scrubbing the battery terminals for a more reliable connection and check for any short circuits. Replace any old batteries that don’t hold a reliable charge. Also, some batteries have an on/off switch. If this is true for your battery, make sure the switch is on. 
4. Check all of your MerCruiser spark plugs. To do so, start by making sure there's an 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.Clean and adjust the spark plugs, replacing any with darkened metal contacts that no longer spark reliably. 
5. If the kill switch isn’t properly attached it could very well be the source of your motor problems. Undo the connection and put it right back into place. The kill switch may need to be replaced altogether.
6. Check your gear shift, as it is easy to knock out of place, preventing the engine from starting. Make sure that you’re in neutral and try starting your engine once more.
7. It may sound obvious, but check for any gas in your fuel tank. This is more common than most boaters think, as a closed vent prevents air from replacing fuel as the motor pulls it out, which is necessary for firing up the engine. On the other hand, an open tank vent can promote evaporation of fuel during storage. 
8. Sometimes, the issues may simply be that your engine propeller has something tangled around it. This may be fishing line, excessive seaweed, or some other material that’s worked its way around the blades. Carefully remove anything that may be wrapped around the propeller, and give it a once-over for any damage that may be present. If the propeller is damaged, it needs to be replaced. Debris around the propeller is the most likely culprit if your boat motor starts, but quickly dies.
9. Pay attention to any anomalies when you last operated your engine. For example, a bogged down engine can indicate failing spark plugs, obstructions in the fuel lines, water infiltration via the head gasket, and more. If you can’t source the issue, consider taking it to a certified Mercury MerCruiser dealer for a full evaluation.

How do I check the hours on my Mercury outboard motor?

Mercury MerCruiser engines are designed with exacting specifications that predictably begin to fail during predetermined time periods. While you should always be keeping track of your engine hours, having an authorized Mercury outboard dealer access your Mercury MerCruiser’s computer memory for a complete diagnostic check about hours of use and other useful data.

A dealer might charge you for 30 minutes or so of labor to run a diagnostic scan, but if you are buying a used Mercury outboard motor, this investment is well worth it. However, if you are negotiating to buy the motor from a certified dealer, the dealer should provide a diagnostics report for no charge.

How often should I change my MerCruiser engine spark plugs?

Most marine mechanics and experienced boaters agree that frequent replacement of spark plugs is absolutely essential for electrical ignitions on MerCruisers. Some boaters are adamant about changing their spark plugs when they break out their boats for the season, while others change their spark plugs every 100 hours. PartsVu recommends regularly inspecting your spark plugs every 100 hours during service intervals, replacing them if they are fouled or damaged, and ALWAYS replacing them every 300 hours (or every 3 years, whichever comes first).

How many hours will my MerCruiser last?

In truth, most well-maintained MerCruiser engines will last anywhere between 5,000 - 12,000 hours - which is why you’ll see MerCruiser engines used in thousands of commercial and recreational boats out on the water . 

Why the wide variance between operational hours? These hours are highly dependent on how much maintenance you’re willing to put into the engine (observing each 100-hour and 300-hour service intervals), what type of use the engine endures (ie. operating under heavy loads or high RPMs for extended periods), and how well the engine is winterized. 

For example, if a Mercury outboard experiences long periods of wide-open throttle, extended periods of trolling, or load weight is commonly higher than recommended, service intervals need to be more frequent, and overall engine life will likely be shorter.

Similarly, improper storage can wreak havoc on your MerCruiser electrical ignition systems. Moisture infiltration corrodes electrical components, where once-reliable electronic ignition systems don’t work at all until all corrosion is removed and all affected components are replaced (including ignition coils and spark plug wires). Improper storage may also enable pests to nest in your engine, where organic matter offsets proper ignition voltages or even small animals may chew wires.