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Knock Sensor 806612T – MerCruiser GM V8 305/350/377
- $96.99
- $96.99
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How to Match This Part
This aftermarket knock (detonation) sensor replaces MerCruiser / Mercury Quicksilver 806612T. It monitors engine vibration for knock and sends a signal so the ECM can retard ignition timing and protect the engine.
Match this part in this order:
1. OEM number on the sensor you are removing or in your parts catalog — 806612T
2. Engine family — MerCruiser MCM / MIE GM V8 marine engines at 305, 350, or 377 CID (5.0L / 5.7L / 6.2L class)
3. Aftermarket cross — Sierra 18-7677 or Mallory 9-33503 if that is what your catalog lists
Confirm the OEM number and engine displacement against your service documentation before ordering. Different MerCruiser ignition / ECM setups can use other knock-sensor numbers.
Part Number Cross-Reference
Use this table to confirm equivalent part numbers. 806612T is the primary MerCruiser reference for this listing.
| Type | Brand | Part Number | Notes |
|---|---|---|---|
| Primary OEM Reference | Mercury / MerCruiser | 806612T | Quicksilver knock sensor |
| Related OEM | Volvo Penta | 3850357, 22024631 | Catalog cross for the same sensor family |
| Related OEM | OMC | 3850357 | Catalog cross for the same sensor family |
| Related OEM | Pleasurecraft (PCM) | R020027 | Catalog cross for the same sensor family |
| Aftermarket | Sierra Marine | 18-7677 | Direct replacement cross |
| Aftermarket | Mallory Marine | 9-33503 | Direct replacement cross |
Part numbers are listed for identification only. This is an aftermarket part manufactured by JLM Marine and is not sold as a genuine Mercury / MerCruiser component.
Compatible Engines
Confirm the MerCruiser engine identification plate and that the removed sensor is numbered 806612T (or a listed cross above). Match by OEM number and GM V8 displacement — do not rely on appearance alone.
| Brand | Application |
|---|---|
| MerCruiser (MCM / MIE) | GM V8 305 CID (5.0L class) |
| MerCruiser (MCM / MIE) | GM V8 350 CID (5.7L class) |
| MerCruiser (MCM / MIE) | GM V8 377 CID (6.2L class) |
Important: This listing is for the 806612T knock-sensor family on the GM V8 displacements above. Other MerCruiser knock sensors exist for different engine families and ECM configurations — verify the OEM number on your engine before ordering.
Technical Specifications
| Specification | Value |
|---|---|
| Part type | Knock / detonation sensor |
| Primary OEM number | 806612T |
| Engine family | MerCruiser MCM / MIE GM V8 |
| Displacements | 305, 350 & 377 CID |
| Aftermarket crosses | Sierra 18-7677; Mallory 9-33503 |
| Function | Detects knock / detonation and signals the ECM for timing retard |
Installation Guide
1
Disconnect the battery. Locate the existing knock sensor on the engine block and note harness routing before unplugging.
2
Remove the old sensor carefully. Keep the mounting threads clean and free of debris so the new sensor seats correctly.
3
Install the new sensor to the torque specified in your MerCruiser service manual for this application. Over- or under-tightening can affect knock detection.
4
Reconnect the harness until fully seated. Route the lead clear of hot manifolds and moving belts.
5
Reconnect the battery. Clear any stored knock-sensor codes if present, then run the engine and confirm normal operation under load.
Note: Professional installation is recommended to ensure safety and optimal performance.
Troubleshooting & FAQ
Why Choose JLM MARINE?
- Precision Fit: Cross-reference matched to MerCruiser 806612T knock-sensor applications on GM V8 305 / 350 / 377 CID marine engines.
- Quality Control: Each batch is inspected for dimensional consistency and workmanship.
- Direct from Manufacturer: Aftermarket marine parts engineered for reliable ignition-knock sensing service.
We can ship to virtually any address in the world with free shipping available for most regions.
For our typical US and Canadian customers , our shipping timeframes are as follows:
- Amazon FBA: orders will be delivered within 1-5 business days after placing the order (during certain special periods such as major promotions, Christmas, etc., the delivery time of Amazon FBA may be affected).
- US warehouse shipment: orders will be delivered within 5 days after placing the order.
- China warehouse shipment: orders will be delivered about 12 days after placing the order.
When you place an order, we will estimate shipping and delivery dates for you based on the availability of your items and the shipping options you choose. Depending on the shipping provider you choose, shipping date estimates may appear on the shipping quotes page.
Please also note that the shipping rates for many items we sell are weight-based. The weight of any such item can be found on its detail page. To reflect the policies of the shipping companies we use, all weights will be rounded up to the next full pound.
Founded in 2002, JLM Marine has established itself as a dedicated manufacturer of high-quality marine parts, based in China. Our commitment to excellence in manufacturing has earned us the trust of top marine brands globally.
As a direct supplier, we bypass intermediaries, which allows us to offer competitive prices without compromising on quality. This approach not only supports cost-efficiency but also ensures that our customers receive the best value directly from the source.
We are excited to expand our reach through retail channels, bringing our expertise and commitment to quality directly to boat owners and enthusiasts worldwide.
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