806612T Knock Sensor for Mercury Mercruiser OMC Volvo Penta | JLM Marine

Knock Sensor for Mercury Mercruiser OMC Volvo Penta | JLM Marine

This knock sensor is engineered to fit GM Small Block marine engines including Mercury Mercruiser, OMC, Volvo Penta, PCM, Marine Power, and Crusader. Designed for GM 305 (5.0L), 350 (5.7L), and 377 (6.2L) V8 engines, this sensor plays a critical role in engine protection by detecting pre-ignition or detonation and signaling the ECM to retard timing, preventing internal damage to pistons and valves.

This sensor directly replaces OEM part number 806612T and crosses with Crusader R020027, Sierra 18-7677, and Volvo Penta 3850357. It installs in the water port located in the middle of the engine block, just above the oil pan on GM Small Block engines.

• Fits GM 305 5.0L, 350 5.7L, and 377 6.2L small block V8 marine engines
• Detects pre-ignition/detonation to prevent engine damage
• Installs in the water port above the oil pan

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 × Knock Sensor (806612T)

Installation Guide

1. Disconnect the negative battery cable to ensure safety during installation.
2. Locate the water port in the middle of the engine block, just above the oil pan.
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 water port.
5. Inspect the mounting area and threads; clean any debris or corrosion if present.
6. Apply a small amount of anti-seize compound to the threads of the new knock sensor (avoid getting compound on the sensor tip).
7. Hand-thread the new knock sensor into the water port to prevent cross-threading.
8. Tighten the sensor to the manufacturer's specified torque (typically 10-15 ft-lbs; consult your service manual).
9. Reconnect the electrical connector to the new knock sensor until it clicks securely.
10. Reconnect the negative battery cable.
11. Start the engine and check for proper operation; verify there are no warning lights or fault codes.
12. Inspect for any leaks around the sensor installation point and re-tighten if necessary.

Troubleshooting & FAQ

Q: How do I confirm this knock sensor fits my engine?
A: Verify that your engine is a GM Small Block V8 (305, 350, or 377 cu. in.) used in Mercury Mercruiser, OMC, Volvo Penta, PCM, Marine Power, or Crusader applications. Cross-reference your current part number with 806612T, Volvo Penta 3850357, Crusader R020027, or Sierra 18-7677.

Q: What are the symptoms of a failing knock sensor?
A: Common signs include engine pinging or knocking under load, reduced power, poor fuel economy, illuminated check engine light, or fault codes related to knock sensor circuit. A faulty sensor cannot properly signal the ECM to retard timing, risking internal engine damage.

Q: Where exactly does this sensor install on my engine?
A: This knock sensor installs in the water port located in the middle of the engine block, just above the oil pan on GM Small Block engines. It threads into the block and connects via an electrical harness.

Q: How often should I replace the knock sensor?
A: Knock sensors typically do not have a fixed replacement interval and are replaced only when they fail or show symptoms. However, if you experience persistent knocking, poor performance, or related fault codes, test and replace the sensor as needed.

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.