392-889925 8M0178581 3859078 Ignition Coil for MerCruiser Volvo 8.1L 496 MAG | JLM Marine

Ignition Coil for MerCruiser Volvo 8.1L 496 MAG – High-Performance Replacement

This aftermarket ignition coil is engineered to fit MerCruiser 8.1L 496 MAG series marine gasoline engines (2001 and newer) and Volvo Penta equivalent models. Designed to meet OEM specifications, it delivers reliable spark energy for consistent engine performance in demanding marine environments.

This coil directly replaces MerCruiser 392-889925 and 8M0178581, as well as Volvo Penta 3859078 and Sierra 18-7493, ensuring broad cross-compatibility with original equipment and popular aftermarket brands.

• Direct replacement for multiple OEM and aftermarket part numbers
• Compatible with MerCruiser 8.1L / 496 MAG marine gasoline engines (2001-Up)
• Single ignition coil unit included

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

Your package includes:

• 1× Ignition Coil

The package contains all parts shown in the product images.

Installation Guide

1. Disconnect the battery negative terminal to prevent electrical shock or short circuits during installation.
2. Locate the faulty ignition coil on your engine block; refer to your service manual or OEM diagrams for exact positioning.
3. Disconnect the electrical connector from the old coil by pressing the release tab and gently pulling it away.
4. Remove the mounting bolt(s) securing the coil to the engine using the appropriate socket or wrench.
5. Carefully lift the old coil off the spark plug boot; twist gently if resistance is felt to avoid damaging the boot.
6. Inspect the spark plug boot for cracks, corrosion, or wear; replace if necessary to ensure proper connection.
7. Position the new ignition coil over the spark plug and press down firmly until fully seated.
8. Reinstall the mounting bolt(s) and torque to manufacturer specifications (typically 8–12 ft-lbs; consult your manual).
9. Reconnect the electrical connector by pushing it onto the coil terminal until you hear or feel a click.
10. Repeat the process for any additional coils if replacing multiple units.
11. Reconnect the battery negative terminal and start the engine to verify proper operation and smooth idle.
12. Check for misfires, rough running, or warning lights; if issues persist, verify all connections and consult a marine technician.

Troubleshooting & FAQ

Q: How do I confirm this ignition coil fits my MerCruiser or Volvo engine?
A: Verify your engine is an 8.1L (496 MAG) series built in 2001 or later. Cross-reference the OEM part numbers listed (392-889925, 8M0178581, or Volvo 3859078) with your current coil or service manual to ensure compatibility.

Q: What are the signs that my ignition coil is failing?
A: Common symptoms include engine misfires, rough idling, loss of power under load, difficulty starting, increased fuel consumption, or a check-engine light. If you experience these issues, test the coil resistance with a multimeter or swap with a known good coil to isolate the problem.

Q: How often should I replace my ignition coils?
A: Ignition coils typically last 3–5 years or 300–500 engine hours, depending on operating conditions. Replace coils if you notice performance issues, or proactively during major tune-ups to prevent unexpected failures on the water.

Q: Can I install this coil myself, or do I need a professional?
A: Installation is straightforward for those with basic mechanical skills and tools. However, if you are unfamiliar with marine electrical systems or lack the proper torque specifications, professional installation is recommended to ensure safety and optimal performance.

Q: Is this an OEM part or an aftermarket replacement?
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.