Description
Sierra 18-8821-1 marine spark plug wire set. Ignition Type: Thunderbolt. Replaces: Mercury Marine 84-816761Q4, 84-816761Q3, 84-816761A17, 84-813720A4, 84-813720A3, 84-816761Q17, 84-816761A4.
About SierraSierra provides premium-quality aftermarket replacements for over 6,000 marine parts, tools, and components. Sierra products are engineered to meet or exceed OEM standards, and stand up in harsh marine environments. Every new Sierra part comes with a limited lifetime warranty that covers the useful life of the product against any defects in workmanship and materials.
![Sudbury Elastomeric Marine Sealant – 10oz Cartridge – White [300]](https://www.durablemarinebattery.com/wp-content/uploads/2026/08/sudbury-elastomeric-marine-sealant-10oz-cartridge-white-300.webp)
![Blue Sea 7605 BatteryLink Charger – 10Amp – 2-Bank[7605]](https://www.durablemarinebattery.com/wp-content/uploads/2026/08/blue-sea-7605-batterylink-charger-10amp-2-bank-7605.webp)
![Rapala Combo Pack – Pliers, Clipper, PunchSharpener [RTC-6PCHS]](https://www.durablemarinebattery.com/wp-content/uploads/2026/08/rapala-combo-pack-pliers-clipper-punchsharpener-rtc-6pchs.webp)
![Whitecap Teak Lumber – 1/2″ x 1-3/4″ x 72″[60813]](https://www.durablemarinebattery.com/wp-content/uploads/2026/08/whitecap-teak-lumber-1-2-x-1-3-4-x-72-60813.webp)
![Ancor Premium Electrical Tape – 3/4″ x 66′ – Orange[334066]](https://www.durablemarinebattery.com/wp-content/uploads/2026/08/ancor-premium-electrical-tape-3-4-x-66-orange-334066.webp)
![Jabsco HotShot HD4 Heavy Duty Washdown Pump – 24V – 4 GPM – 60 PSI [Q402J-118N-3A]](https://www.durablemarinebattery.com/wp-content/uploads/2026/08/jabsco-hotshot-hd4-heavy-duty-washdown-pump-24v-4-gpm-60-psi-q402j-118n-3a.webp)
![Ancor 24-22 Gauge Heat Shrink Step-Down Multi-Wire Connectors – 25-Pack[320025]](https://www.durablemarinebattery.com/wp-content/uploads/2026/08/ancor-24-22-gauge-heat-shrink-step-down-multi-wire-connectors-25-pack-320025.webp)