ACDelco MR43T Marine Resistor Spark Plug | GM Inboard & Sterndrive
Free returns on all eligible orders
You have 30 days to request a return. All sale items are final sale.
ACDelco Marine Resistor Spark Plug for GM Inboard & Sterndrive Engines
The ACDelco MR43T is a marine-specific resistor spark plug for GM-based inboard and sterndrive engines. Like all ACDelco “MR” marine plugs, the built-in resistor suppresses radio frequency interference (RFI) to protect onboard electronics including GPS units, chartplotters, and VHF radios. The MR43T features a tapered seat design and is a distinct specification from the MR43LTS. Sold individually.
Compatible Applications
- GM-based marine inboard and sterndrive engines requiring ACDelco MR43T spark plug
- MerCruiser, Crusader, and Indmar GM-block engines — verify OEM plug number before ordering
Key Features
- Marine-specific resistor design — suppresses RFI to protect onboard electronics
- Tapered seat design — distinct from the MR43LTS (gasket seat)
- Copper core center electrode for reliable spark across a wide operating range
- Sold individually
Parts Desk Insights
The MR43T is a standard marine resistor plug for GM-based inboard and sterndrive engines — the tapered seat is the key physical difference from the ACDelco MR43LTS, and the two are not interchangeable. Always verify your engine’s OEM plug specification before ordering, as using the wrong seat type can cause improper sealing and heat transfer issues. The resistor is required on marine engines to prevent ignition noise from interfering with navigation and communication electronics. It’s the right plug for routine tune-ups on compatible GM marine engines and a reliable baseline before considering an upgrade to platinum or iridium.
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.