Mercury MerCruiser NGK Spark Plug ITR4A15 8M0204739 4-pack
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Mercury MerCruiser / Quicksilver NGK Spark Plug – ITR4A15 (8M0204739)
Maintain strong ignition performance with the genuine Mercury Marine / Quicksilver 8M0204739 NGK ITR4A15 Laser Iridium Spark Plug. This OEM spark plug is designed for select MerCruiser V6 and V8 engines, delivering reliable ignition, improved combustion efficiency, and long service life in demanding marine environments.
The Laser Iridium center electrode provides precise spark and exceptional durability, while the copper core and ceramic insulator help dissipate heat and maintain consistent engine performance.
Key Features
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Genuine Mercury / Quicksilver OEM NGK spark plug
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Laser Iridium electrode for long service life and consistent spark
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Copper core improves heat dissipation and combustion efficiency
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Corrosion-resistant construction for marine environments
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Pre-gapped to manufacturer specifications for easy installation
Part Details
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OEM Part Number: 8M0204739
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NGK Model: ITR4A15 (Stock No. 5599)
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Product Type: Iridium spark plugSuperseded / Cross-Reference
- 4 pack
This plug replaces earlier Mercury part numbers including:
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884019
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884019001
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8M2018369
Compatible Mercury MerCruiser Engines
Commonly used on MerCruiser MPI sterndrive and inboard engines, including:
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4.3L V6 MPI engines
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5.0L V8 MPI engines
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5.7L V8 MPI engines
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6.2L V8 MPI engines
These engines are typically equipped with ECM 555 ignition systems in many 2001+ applications.
Performance Benefits
Iridium spark plugs produce a stronger and more stable spark, which can improve engine starting, maintain smoother idle, and provide more efficient combustion across the RPM range.
Important Compatibility Note
Spark plug type and heat range vary by engine model, ignition system, and serial number range. Always verify compatibility using the engine serial number or owner’s manual specification before ordering.
Shipping: Ships same or next day for fast Canada wide shipping.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 3–4 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.