7" Spark Plug Wire – Fits Mercury Marine 150-200 HP Outboard Motors (Replaces 18-8819)

7" Spark Plug Wire – Fits Mercury Marine 150-200 HP Outboard Motors (Replaces 18-8819)

This 7-inch spark plug wire is designed for Mercury Marine 150-200 HP V6 outboard motors (1970-1988), including V-150, V-175, and V-200 series engines. It provides a reliable, high-performance connection between the ignition coil/distributor and the spark plug.

This component serves as a direct replacement for Sierra part number 18-8819 and multiple Mercury Marine OEM part numbers, ensuring a precise fit and restoring original performance for your engine's ignition system.

• Marine-Grade Durability: Constructed with silicone insulation and stainless steel components to resist heat, saltwater corrosion, vibration, and fuel exposure.
• Direct Fit Installation: Designed as a direct replacement part, featuring a terminal end for the coil/distributor and a boot end for the spark plug for a straightforward installation.
• Precise Length: This wire is 7 inches (178 mm) long. Please verify the required length for your specific cylinder, as other lengths may be necessary.

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

• 1 x 7" Spark Plug Wire (Replaces 813715A1, 90816A25)

Installation Guide

1. Ensure the engine is completely off, cool to the touch, and the boat's battery is disconnected.
2. Identify the specific spark plug wire you intend to replace. Work on one wire at a time to avoid mixing up connections.
3. Firmly grasp the boot at the spark plug end, twist it gently to break the seal, and pull it straight off the plug.
4. Trace the wire back to the distributor or coil, grasp the boot, and pull it straight off the terminal.
5. Compare the new spark plug wire with the old one to confirm an identical match in length and connector types.
6. Lightly apply dielectric grease to the inside of both boots on the new wire to ease installation and improve sealing.
7. Press the distributor/coil boot onto its terminal until you feel it click into place.
8. Route the new wire along the same path as the original, then press the spark plug boot firmly onto the spark plug until it seats securely.
9. Reconnect the boat's battery, start the engine, and check for smooth operation.

Troubleshooting & FAQ

Q: How do I confirm this wire fits my specific engine cylinder?

A: This is a 7-inch wire. While it fits the listed V6 models, different cylinder positions may require different lengths (e.g., 5", 9", or 12"). Always measure your old wire or consult your owner's manual to confirm the required length before ordering to ensure correct fitment.

Q: What are common signs of a failing spark plug wire?

A: Symptoms of a bad wire include engine misfires (especially under load), rough idling, difficulty starting, reduced acceleration, and decreased fuel efficiency. You may also see visible damage like cracks in the insulation, burn marks, or corrosion on the terminals.

Q: How often should I replace my spark plug wires?

A: There is no universal replacement interval, but it is good practice to inspect them for damage during regular maintenance and consider replacing them every few seasons or when you replace your spark plugs, especially in a harsh saltwater environment.

Q: Is this an OEM or aftermarket part?

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.