Spark Plug Ignition Coil Wire Set – Fits Mercruiser 5.0L, 5.7L, 6.2L MPI V8 Engines (Replaces 84-863656A1, 18-8828)

Spark Plug Ignition Coil Wire Set – Fits Mercruiser 5.0L, 5.7L, 6.2L MPI V8 Engines

This spark plug ignition wire set is designed for Mercruiser MPI engines including the 5.0L, 5.7L, and 6.2L V8 sterndrive and inboard motors. It is compatible with models that use a flat cap distributor, primarily manufactured from the late 1990s through the mid-2000s.

This kit serves as a direct replacement for Mercruiser part number 84-863656A1, Sierra 18-8828, and others, ensuring a precise fit and reliable performance for your marine engine's ignition system.

• Installation Method: Direct Fit Replacement
• Included Components: The set contains 8 spark plug wires and 1 coil wire for a complete installation.
• Durable Construction: Built with silicone housing and stainless steel conductors to resist heat, vibration, and corrosion common in marine environments.

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below. For Mercury owners, here’s a guide to help you identify your engine’s serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

Technical Specifications

Package Contents

This ignition wire set includes the following components:

• 2x Spark Plug Wires — 22 inches (55.9cm)
• 2x Spark Plug Wires — 27 inches (68.6cm)
• 2x Spark Plug Wires — 31 inches (78.7cm)
• 2x Spark Plug Wires — 36.5 inches (92.7cm)
• 1x Coil Wire — 21 inches (53.3cm)

Installation Guide

1. Safety First: Disconnect the boat's battery before beginning any electrical work to prevent accidental shocks or shorts.
2. One at a Time: To avoid mixing up firing order, replace one spark plug wire at a time. Start with the shortest wire, remove the old one, and match its length to a new one from the kit.
3. Distributor Cap Connection: Firmly press the new wire's boot onto the correct terminal on the distributor cap until it clicks into place.
4. Spark Plug Connection: Route the wire to the corresponding spark plug, ensuring it follows the original path and is clear of hot or moving parts. Push the boot onto the spark plug until it seats securely.
5. Repeat Process: Continue this process for all remaining spark plug wires and the coil wire.
6. Final Check: Once all wires are replaced, double-check that each connection is secure at both the distributor and the spark plug. Reconnect the battery and start the engine to test for smooth operation.

Troubleshooting & FAQ

How do I confirm this fits my engine?
First, check the compatibility table on this page. This set is for Mercruiser 5.0L, 5.7L, and 6.2L MPI V8 engines with a flat cap distributor. Cross-reference your engine's original wire set part number with those listed, such as Mercruiser 84-863656A1 or Sierra 18-8828.

What are the signs my old ignition wires are failing?
Common symptoms of bad spark plug wires include engine misfires (especially under load), rough idling, decreased power, poor fuel economy, and visible signs of wear like cracks, burns, or corrosion on the wire boots or jackets.

What lengths are the wires in this kit?
The set contains a total of nine wires: two 22", two 27", two 31", two 36.5", and one 21" coil wire. This variety ensures a proper fit for all cylinders on compatible V8 engines.

OEM vs. Aftermarket?
This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

How fast do you ship and how much does it cost?
We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

What is your warranty and return policy?
This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.