Mercury 8M0079202 – Ignition Coil Kit | Thunderbolt IV & V | MerCruiser V6 & V8
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Mercury 8M0079202 – Ignition Coil Kit | Thunderbolt IV & V | MerCruiser V6 & V8
Part Number: 8M0079202
Mercury Reference: 300-8M0079202
Brand: Mercury Marine
Official Product Type: Ignition Coil Kit
System: Thunderbolt IV / Thunderbolt V Ignition
Voltage: 12V
Supersedes: 392-7803A4, 392-805570A2
About This Part
Mercury 8M0079202 is a genuine OEM ignition coil kit for MerCruiser GM-based gasoline engines equipped with Thunderbolt IV or Thunderbolt V ignition systems. The ignition coil transforms 12-volt battery power into the high-voltage charge needed to fire the spark plugs. A failing coil causes misfires, hard starting, rough idle, and power loss — replacing it with a genuine OEM unit restores consistent spark delivery and reliable engine operation in the demanding marine environment.
Compatible Applications
For use on MerCruiser GM-based gasoline engines with Thunderbolt IV or Thunderbolt V ignition. Always verify using your engine model and serial number before ordering.
- MerCruiser 4.3L V6 (Thunderbolt IV / V)
- MerCruiser 5.0L V8 (Thunderbolt IV / V)
- MerCruiser 5.7L V8 / 350 MAG (Thunderbolt IV / V)
- MerCruiser 6.2L V8 (Thunderbolt IV / V)
- MerCruiser 7.4L V8 / 454 MAG (Thunderbolt IV / V)
- MerCruiser 8.2L V8 / 502 MAG (Thunderbolt IV / V)
- Sterndrive and inboard applications using the above engine families
Serial Number & Fitment Notice
Ignition components vary by engine model, ignition system type, and serial number range. Confirm the correct coil for your specific engine using the Mercury parts catalog with your engine model and serial number before ordering. Not all MerCruiser V6 and V8 engines use the same ignition coil.
Supersession & Cross-Reference
- Current OEM Part Number: 8M0079202
- Supersedes: 392-7803A4, 392-805570A2
- Aftermarket Cross-Reference: Sierra 18-5438, CDI Electronics E18-0008
When to Replace
Replace the ignition coil when the engine shows any of the following:
- Hard starting or failure to start
- Engine misfires or rough idle
- Loss of power under load
- Intermittent spark or ignition cutout
- Failed ignition system diagnostic
- Visible coil damage, cracking, or carbon tracking
Service Interval
The ignition coil does not have a fixed replacement interval — it is a condition-based replacement item. It is good practice to inspect ignition components during annual tune-up service and replace proactively if the coil shows signs of age, heat damage, or degraded output. Many technicians replace the coil as part of a complete ignition service alongside spark plugs, distributor cap, and rotor.
Installation Notes
Disconnect the battery before beginning any ignition work. Inspect the coil mounting bracket, primary and secondary wiring connectors, and distributor connections before installation. Ensure all connections are clean and fully seated. After installation, verify spark output and confirm smooth engine starting and idle before returning to service.
Parts Desk Insights
Best Use Case: This coil is the right choice for a complete ignition service on a Thunderbolt IV or V equipped MerCruiser. It pairs well with a distributor cap, rotor, spark plugs, and plug wires for a full tune-up. Customers doing a full ignition refresh get the best results replacing all wear items at the same time rather than chasing individual components.
Common Mistakes: The most frequent error is ordering by engine displacement alone without confirming the ignition system type. Not all MerCruiser V8s use Thunderbolt ignition — later engines transitioned to different systems, and the coil is not compatible across ignition types. Always confirm Thunderbolt IV or V fitment using the engine serial number. A second common mistake is reusing old ignition wiring connectors that have corroded or heat-damaged terminals — a new coil on a degraded harness will underperform and can be misdiagnosed as a repeat coil failure.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 1-3 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.