Spark Plug Wire Set – Fits Mercruiser 120/140/2.5L/3.0L GM Sterndrive (Replaces 816761A5, 816761Q5)

Spark Plug Wire Set – Fits Mercruiser 120/140/2.5L/3.0L GM Sterndrive

This aftermarket spark plug wire set is designed for Mercruiser GM inline 4-cylinder engines (120, 140, 2.5L, and 3.0L) manufactured between 1983 and 1995, including sterndrive applications. It provides a reliable, direct-fit replacement to restore ignition performance.

This set is a direct replacement for multiple OEM and aftermarket part numbers, including Mercruiser 816761A5, 816761Q5, 813720A5, and 816761K5, ensuring broad compatibility.

• Engineered as a direct replacement for straightforward installation.
• Constructed with a Kevlar core, stainless steel conductor, and high-temperature silicone insulation for durability.
• The package includes a complete set of 5 ignition wires of varying lengths to match engine requirements.

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.

Technical Specifications

Package Contents

The Spark Plug Wire Set includes:

• 1 x Spark Plug Wire (45.5cm / 17.9 inch)
• 1 x Spark Plug Wire (36cm / 14.2 inch)
• 2 x Spark Plug Wire (30.7cm / 12.1 inch)
• 1 x Spark Plug Wire (29.5cm / 11.6 inch)

Installation Guide

1. Safety First: Ensure the engine is cool and the battery is disconnected before starting.
2. Note Wire Order: Note the routing of the existing spark plug wires from the distributor cap to each spark plug. Taking a photo can be helpful.
3. Remove Wires One by One: To avoid mixing up the firing order, replace one wire at a time. Gently twist and pull the boot to remove it from the spark plug and distributor cap.
4. Match and Install New Wires: Match the length of the new wire to the old one. Apply a small amount of dielectric grease to the inside of each boot for a better seal and easier future removal.
5. Secure Connections: Push the new boots firmly onto the spark plug and distributor cap until you feel them click into place.
6. Check Routing: Ensure wires are routed correctly and secured in any factory clips or looms to prevent contact with hot engine parts or sharp edges.
7. Final Check: Once all wires are replaced, reconnect the battery and start the engine to confirm it runs smoothly.

Troubleshooting & FAQ

Q: How do I confirm this wire set fits my engine?
A: The best way is to check your engine's serial number and model against the "Compatible Engine Models" table. You can also match the part number (e.g., 816761A5) from your old wires or service manual with our "Part Number Cross-Reference" list.

Q: What are the signs that my spark plug wires need replacing?
A: Common symptoms include engine misfires, rough idling, poor acceleration, reduced fuel economy, and visible signs of wear on the wires, such as cracks, burns, or corrosion on the terminals.

Q: Why do the wires have different materials like Kevlar and silicone?
A: The Kevlar core provides high tensile strength to prevent stretching or breaking. The silicone insulation and boots offer excellent protection against high temperatures, moisture, oil, and abrasion, ensuring reliable electrical performance.

Q: OEM vs. Aftermarket?
A: 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.

Q: How fast do you ship and how much does it cost?
A: 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.

Q: What is your warranty and return policy?
A: 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.