Mercury – Quicksilver 816761Q4 Spark Plug Wire Kit | V8 GM MerCruiser (LH) Engines (305 & 350 CID) | Thunderbolt IV Ignition | 816761Q4

Overview

When your boat starts instantly and runs smooth, that’s good spark at work. The Quicksilver 816761Q4 Spark Plug Wire Kit keeps that spark steady in V8 left-hand rotation MerCruiser engines (305 and 350 CID) equipped with Thunderbolt IV ignition systems (1981–1992).

Each wire in this OEM kit is built to exact Mercury specs — the right length, perfect resistance, and tight-fitting boots that keep moisture out. Made for life on the water, these wires hold up to heat, salt, and vibration, giving your engine a strong, consistent spark every time you fire it up.

Key Features

• Purpose: Replaces old or worn plug wires to restore clean, consistent ignition.
• Fitment: Designed for V8 LH GM-based MerCruiser engines (305 & 350 CID) with Thunderbolt IV ignition systems (1981–1992).
• Kit Contents: Eight spark plug wires with molded plug-end boots for a secure, water-resistant connection.
• Design: Each wire is factory-length, cut precisely for the correct routing and plug reach.
• Marine Durability: Engineered for heat, moisture, and vibration resistance in tough marine environments.

Engine & Boat Compatibility

• Left-hand rotation GM-based V8 MerCruiser engines (305 & 350 CID)
• Thunderbolt IV ignition systems (1981–1992)
• Common in sport cruisers, inboard/outboard boats, and classic tow setups

Performance & Practical Benefits

The 816761Q4 kit gives your ignition system a fresh start. The low-resistance cores keep spark voltage strong, ensuring smooth idle, quick starts, and crisp throttle response. Whether you’re idling through the marina or running at full plane, these wires keep every cylinder firing evenly.

The marine-grade insulation resists cracking and moisture, even after years of exposure. Each boot grips tight for a leak-free seal, so the spark energy goes where it’s supposed to — not lost to arcing or corrosion. You’ll feel smoother running and more consistent power from the first turn of the key.

Why Buy OEM

Mercury’s OEM plug wires are built for the demands of marine engines — constant movement, salt exposure, and high operating temperatures. Aftermarket wires might fit, but they often use weaker insulation or generic resistance values that cause premature failure.

A genuine Quicksilver wire set gives you the right lengths, proper resistance, and long-lasting durability. It’s the same quality your engine was built with — tested, proven, and made to last season after season.

FAQ

Q1: What engines fit the Quicksilver 816761Q4 kit?
A: It fits V8 left-hand rotation GM-based MerCruiser engines (305 & 350 CID) with Thunderbolt IV ignition systems (1981–1992).

Q2: How many wires are included?
A: The kit includes eight spark plug wires, all pre-fitted with molded boots.

Q3: Are they saltwater safe?
A: Yes. The wires and terminals are built from corrosion-resistant materials designed for marine use.

Q4: How difficult is installation?
A: Easy. Replace one wire at a time to maintain firing order — no special tools needed.

Q5: Why OEM instead of aftermarket?
A: OEM wires fit perfectly, resist marine wear, and provide steady spark — aftermarket versions can’t match the consistency.