Champion RN12YC Spark Plug | #404 | 4-Pack | MerCruiser, Sterndrive & Marine Inboard
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A Trusted Spark Plug for Marine Inboard and Sterndrive Engines — 4-Pack.
The Champion RN12YC is a projected-tip, resistor-type spark plug widely used in marine inboard and sterndrive engines, including MerCruiser and Volvo Penta applications. Part number 404, the YC-series design features a projected tip for improved ignitability and a built-in resistor to suppress radio frequency interference — important in the marine environment where electronics and communication equipment are in close proximity to the engine.
Sold in a 4-pack (Champion part 44122). Always verify fitment against your engine's owner's manual or Champion application guide before ordering.
Key Features
- Champion RN12YC spark plug — 4-pack (Champion #404)
- Projected tip for improved ignitability and combustion efficiency
- Built-in resistor suppresses radio frequency interference (RFI)
- Copper core electrode for reliable heat transfer and consistent spark
- Widely used in marine inboard and sterndrive engine applications
Compatible Applications
- MerCruiser sterndrive engines specifying Champion RN12YC or equivalent
- Volvo Penta inboard and sterndrive engines specifying Champion RN12YC or equivalent
- GM/Chevrolet V8-based marine inboard engines specifying RN12YC or equivalent
- Other marine inboard and sterndrive engines cross-referencing Champion #404 or part 44122
- Verify fitment using your engine's owner's manual or the Champion spark plug application guide
Parts Desk Insights
The RN12YC is the go-to plug for MerCruiser and Volvo Penta sterndrive tune-ups on GM V8-based engines. If you're doing a full inboard or sterndrive service, replace all plugs at the same time — uneven plug wear across cylinders is a common cause of rough idle and inconsistent performance. Marine inboard engines typically run harder and hotter than automotive equivalents, so sticking to the OEM-specified plug type and heat range matters more than it might in a car.
For other ignition components for MerCruiser and sterndrive engines, see the ARCO 12V Starter Solenoid for Mercury/MerCruiser or browse our Ignition Components collection. For NGK alternatives in marine inboard applications, see the NGK BPR6ES.
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.