Sierra 18-8821-1 MerCruiser Thunderbolt V8 Spark Plug Wire Set

The Sierra 18-8821-1 is a premium spark plug wire set engineered specifically for MerCruiser V8 marine engines with Thunderbolt ignition systems. This complete wire set is designed for 350 Mag Ski and 5.0L Alpha and Bravo (Gen+) applications, delivering reliable ignition performance in demanding marine environments.

Key Features:

• Complete set includes coil wire plus 8 spark plug wires in varying lengths: two 29-inch, two 34-inch, two 38-inch, two 44-inch wires, and one 12-inch coil wire
• Kevlar core construction provides maximum durability and extended service life
• 8mm high-tear-strength silicone jacket protects conductors up to 500°F
• Durable stainless steel wound conductor maximizes horsepower and engine performance
• Premium silicone boots and jacketing offer superior high-temperature protection
• Corrosion-resistant stainless steel snap-lock terminals for maximum conductivity
• Superior RFI/EMI suppression protects GPS, VHF, and electronic engine controls
• Posi-lock terminals resist corrosion and prevent terminal pull-off

Sierra replacement parts are designed to meet or exceed OEM specifications. This wire set replaces MerCruiser part numbers 84-816761Q3, 84-816761Q4, 84-816761Q17, 84-816761A4, 84-816761A17, 84-813720A3, and 84-813720A4. The exact-fit design ensures straightforward installation and years of trouble-free operation.