3854905 Knock Sensor Assembly for Volvo Penta OMC | JLM Marine

Knock Sensor Assembly – Fits Volvo Penta & OMC Cobra Sterndrive Marine Engines

This aftermarket Marine Knock Sensor Assembly is designed for Volvo Penta stern drive and OMC Cobra sterndrive marine engines. Engineered to detect engine knock and optimize ignition timing, this sensor ensures smooth performance and engine protection in marine applications.

Directly replaces OEM part numbers Volvo Penta 3854905, OMC Cobra 3854905, Sierra 18-7679, and Mallory 9-33504, providing a reliable and cost-effective solution for your sterndrive engine maintenance.

• Compatible with Volvo Penta and OMC Cobra sterndrive engines
• Direct replacement for multiple OEM and aftermarket part numbers
• Precision-engineered for marine engine knock detection

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

This package contains the following component:

• 1 × Marine Knock Sensor

Installation Guide

1. Disconnect the negative battery cable to ensure safety during installation.
2. Locate the existing knock sensor on your Volvo Penta or OMC Cobra sterndrive engine block.
3. Disconnect the electrical connector from the old knock sensor.
4. Using an appropriate wrench or socket, carefully unscrew and remove the old knock sensor from the engine.
5. Clean the mounting surface on the engine block to ensure proper contact and seal.
6. Install the new knock sensor by threading it into the mounting hole hand-tight first.
7. Torque the sensor to the manufacturer's recommended specification (typically 15–20 ft-lbs; consult your service manual).
8. Reconnect the electrical connector to the new knock sensor, ensuring a secure fit.
9. Reconnect the negative battery cable.
10. Start the engine and verify proper operation with no warning lights or performance issues.

Troubleshooting & FAQ

Q: How do I confirm this knock sensor fits my engine?
A: Verify your engine is a Volvo Penta stern drive or OMC Cobra sterndrive model. Cross-reference your current part number with those listed (3854905, Sierra 18-7679, Mallory 9-33504) to confirm compatibility.

Q: What are the signs that my knock sensor needs replacement?
A: Common symptoms include engine pinging or knocking under load, reduced power, poor fuel economy, check engine light illumination, or stored knock sensor fault codes in the engine computer.

Q: How often should I replace the knock sensor?
A: Knock sensors typically last many years, but should be replaced immediately if fault codes appear or if engine knocking occurs. Inspect during routine engine servicing or if performance issues arise.

Q: Can I install this sensor myself or do I need a mechanic?
A: Installation is straightforward for those with basic mechanical skills and tools. However, proper torque specifications and electrical connector care are critical, so professional installation is recommended if you're unsure.

Q: Is this an OEM part or 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.