Mercury – 815407T5 Ignition Rotor and Cap Kit | V6 GM MerCruiser Engines | Thunderbolt IV & V HEI Ignition | 815407T5

Overview

When your engine lights up instantly and runs smooth from idle to plane, you’re hearing the sound of a healthy ignition system. The Mercury 815407T5 Ignition Rotor and Cap Kit helps keep it that way. Built for marinized GM-based V6 MerCruiser engines with Thunderbolt IV and V HEI ignition systems, this kit restores strong, consistent spark delivery and smooth throttle response.

Salt air, vibration, and heat can wear down the ignition cap and rotor over time. This genuine Mercury kit replaces both, giving your engine the crisp, even spark it needs to run its best — without radio interference or timing hiccups.

Key Features

• Purpose: Replaces worn or corroded ignition cap and rotor to restore steady spark and dependable performance.
• Fitment: Designed for marinized GM V6 MerCruiser engines with Thunderbolt IV and V HEI ignition systems.
• Kit Contents: Includes a distributor cap, gasket, and coated brass rotor blade for a complete replacement.
• Construction: Rotor and contacts coated to resist RFI interference and electrical pitting in marine environments.
• OEM Quality: Built to Mercury Marine factory specs for perfect fit and long-term reliability.

Engine & Boat Compatibility

• GM-based V6 MerCruiser sterndrive and inboard engines
• Thunderbolt IV and V HEI ignition systems
• Common on cruisers, runabouts, and mid-size performance boats

Performance & Practical Benefits

The 815407T5 kit helps your engine fire up cleanly and run smoother throughout the RPM range. The brass rotor blade and terminals provide sharp, consistent spark delivery, while the coated contacts minimize RFI interference — so your GPS, radios, and sound systems stay clear.

Replacing a worn cap and rotor can eliminate rough idle, misfires, and hesitation when accelerating. Once installed, you’ll notice easier starts, a steadier tone at cruise, and better reliability every time you hit the water. It’s a small maintenance job with a big payoff in performance and peace of mind.

Why Buy OEM

Mercury OEM ignition parts are purpose-built for marine duty — constant heat, vibration, and moisture that would quickly wear down automotive parts. Each cap and rotor is made to exact tolerances, ensuring proper fit, sealing, and spark timing.

Aftermarket kits often use lower-grade materials or looser tolerances that lead to poor spark quality and early failure. With Mercury, you’re getting a proven design that’s been tested in saltwater, heat, and real-world boating conditions.

FAQ

Q1: What engines does the Mercury 815407T5 fit?
A: It’s made for V6 GM-based MerCruiser engines with Thunderbolt IV and V HEI ignition systems.

Q2: What comes in the box?
A: One distributor cap, one rotor, and one gasket — all OEM Mercury components.

Q3: Will it reduce electronic interference?
A: Yes. The coated rotor and brass contacts are designed to resist RFI interference with your onboard electronics.

Q4: Is it good for saltwater?
A: Absolutely. The materials and coatings are engineered for marine environments, preventing corrosion and arcing.

Q5: How often should I replace the cap and rotor?
A: Inspect every 100 hours or annually. Replace if you notice corrosion, pitting, or ignition issues.