Sierra 18-8837-1 Spark Plug Wire Set for MerCruiser Stern Drive Engines

The Sierra 18-8837-1 is a premium marine-grade spark plug wire set engineered as a direct replacement for MerCruiser stern drive engines equipped with Thunderbolt ignition systems. Built to meet or exceed OEM specifications, this set replaces Mercury Marine part number 84-847701A7 and is constructed from high-quality materials specifically designed for the demanding marine environment.

Each wire set features Sierra's application-specific magnetic suppression core, which minimizes electromagnetic interference for clean engine operation and reliable ignition performance. A Kevlar-reinforced core adds exceptional tensile strength and resistance to stretching, ensuring long service life even under high-vibration marine conditions. The stainless steel wound conductor delivers consistent, low-resistance spark delivery for maximum horsepower and engine efficiency.

Key Features:

• Application-specific magnetic suppression core minimizes ignition interference
• Kevlar core construction for maximum durability and long service life
• Stainless steel wound conductor for optimal conductivity and maximum horsepower
• High-temperature silicone jackets and boots resist heat, moisture, and grime
• OE-style boots lock out heat, dirt, and corrosion
• Meets or exceeds OEM specifications
• Ignition type: Thunderbolt, 8-cylinder
• Includes 8 spark plug wires and 1 coil wire

Designed for MerCruiser 420, 425, 465, 500, 500 Bulldog, 525SC, and 600SC engines with 8-cylinder Thunderbolt ignition. Replaces Mercury Marine OEM part number 84-847701A7. Cross-reference numbers: 47-8837-1, 47-88371, 18-8837.