Mercury MerCruiser Knock Sensor 806612T

Mercury MerCruiser Knock Sensor 806612T

The Mercury MerCruiser 806612T is a genuine OEM engine knock sensor used on select GM-based MerCruiser gasoline engines. The sensor detects abnormal combustion vibration and provides the engine-management system with the information needed to respond to spark knock or detonation.

Compatible Applications

• 5.0L / 305 V8
• 5.7L / 350 V8
• 350 MAG
• 350 MAG EFI / MPI
• MX 6.2L MPI
• Carbureted, EFI, and MPI configurations where 806612T is specified

Mercury catalog data shows use across numerous sterndrive, inboard, and ski-engine configurations with different serial ranges. Confirm your engine serial number and electrical-system diagram before ordering, since MerCruiser used different knock sensors, modules, and wiring arrangements across similar GM engine families.

Part Details

• Part number: 806612T
• Brand: Mercury Marine
• Official product type: Knock sensor
• System: Engine management / ignition
• Quantity: 1 per applicable engine
• GTIN: 745061283732

Related Parts

• 805218T Engine temperature sensor
• 805592A1 Connector assembly
• 8067051 Y-fitting
• 864388 Harness adapter on applicable assemblies

When This Part Needs Replacement

Replace the sensor when diagnostic testing identifies a failed or unreliable knock-sensor signal, when the connector or sensor body is damaged, or when corrosion prevents a secure electrical connection. Knock-related faults can also originate from wiring, connectors, ignition components, or abnormal engine operation.

Installation Notes

Install in the original engine location shown in the Mercury parts diagram. Inspect the electrical connector and harness before fitting the replacement sensor. Applicable diagrams show 806612T alongside temperature sensor 805218T and associated engine harness components.

Alternate/Superseded Part Numbers

• 806612T current Mercury OEM part number
• No verified superseding part number

Technical FAQ

What happens if this sensor fails? A failed knock sensor can cause the engine-management system to lose detonation protection, leading to reduced performance or fault codes.

How do I know this is the right sensor for my engine? If you are unsure, confirm your engine serial number and electrical-system diagram, since several MerCruiser V8 families look nearly identical externally but use different electronic-control components.

Parts Desk Insights

Best use case: This sensor is the right replacement when diagnostic testing points to a failed or unreliable knock signal on a GM-based MerCruiser gasoline engine.

Common mistake: The most common mistake is matching by engine displacement alone. Several MerCruiser V8 families look nearly identical externally but use different knock sensors and wiring arrangements, so the engine serial number is the safer match point.

Sizing and fitment: If you are replacing this sensor, inspect the connector and harness at the same time, since 806612T is commonly installed alongside temperature sensor 805218T on the same harness.