Mercury – ACDelco Double Platinum Spark Plug | Ignition System | Nickel Alloy & Copper Core | 8M0129146

Overview

There’s a particular kind of comfort that comes from an engine that fires immediately—no hesitation, no uneven rumble, just a clean, confident start that tells you the day’s going to go right. That feeling isn’t accidental. It comes from parts like the Mercury 8M0129146 ACDelco GM Original Equipment Double Platinum Spark Plug doing their job exactly as they should. When you’re pushing a heavy MerCruiser through chop or easing into a tight marina, you want ignition you can trust every single time. This spark plug brings that kind of reliability—quietly, consistently, and without drama.

Key Features

• Double platinum spark plug engineered for long-lasting ignition performance
• Nickel alloy tip and copper core construction for stable conductivity
• Ribbed suppressor seal designed to reduce misfires and improve acceleration
• Built to match OEM specifications for MerCruiser 496 Mag, 496 Mag HO, and MIE 8.1L engines
• Designed for full replacement rather than cleaning or refurbishing

Engine & Boat Compatibility

• Fits MerCruiser 496 Mag sterndrive engines
• Fits MerCruiser 496 Mag HO engines
• Fits MerCruiser MIE 8.1L and 8.1L HO inboard engines
• Ideal for cruisers, sport boats, performance sterndrives, and larger offshore fishing boats

Performance & Practical Benefits

When your spark plugs are fresh and properly matched to your engine, everything feels better. The throttle response tightens up. Starts become quick and predictable. And on long runs, you’ll feel the engine settle into that smooth, steady rhythm that only a well-maintained ignition system delivers.

The 8M0129146 plug uses a copper core for consistent thermal control, which is crucial in big-block marine engines that run hot under load. The double platinum pads help the plug resist wear over hundreds of hours, delivering crisp ignition even after countless cycles. It’s the kind of part you install once and trust season after season.

You’ll also notice fewer small annoyances—reduced sputtering, cleaner idle, and better fuel burn. Big displacement engines rely heavily on spark quality, and a tired plug can steal power without you immediately realizing it. With this Mercury Marine part, the difference feels real: cleaner combustion, steadier pull, and reliable performance whether you’re cruising at low speed or climbing onto plane.

Why Buy OEM

Ignition isn’t a place to gamble. Mercury’s OEM spark plugs are built to match the engine’s heat range, firing demands, and design tolerances precisely. Aftermarket options may look similar, but differences in resistance, tip material, or heat control can cause fouling, rough idle, or even long-term engine damage.

Choosing the genuine ACDelco/Mercury plug gives you:

• The correct heat range for your specific block
• Maximum durability under marine load
• Factory-level performance and efficiency
• A simple, stress-free replacement process

If you’re already pulling the cowl or hatch to replace plugs, replacing all of them together ensures even performance across cylinders and prevents chasing issues later.

FAQ

Q1: Which Mercury engines does the 8M0129146 spark plug fit?

It fits MerCruiser 496 Mag, 496 Mag HO, and MIE 8.1L & 8.1L HO engines.

Q2: What makes this spark plug better than aftermarket versions?

It’s built to exact OEM specs with double platinum durability, proper heat range, and materials designed specifically for marine use.

Q3: How do I know it’s the right plug for my engine?

Check your owner’s manual—use only the plug listed by Mercury for your specific model.

Q4: Can this plug be used in both saltwater and freshwater environments?

Yes. The materials and construction are designed to resist marine corrosion and maintain stable performance.

Q5: Is installation straightforward?

Most boat owners with basic mechanical experience can replace plugs easily. Just replace all plugs at the same time for best results.