Fits MCM V-6 & V-8 (305, 350 & 496 cid) MPI engines with ECM 555. Unnoticed engine knock can quickly turn into serious damage, making the Mercury Knock Sensor (8M6003194) a critical component in keeping your MerCruiser running at peak performance. This sensor continuously monitors vibrations, detecting detonation before it becomes a problem. By sending real-time data to the ECM 555, it allows the engine to fine-tune timing for smoother operation, better fuel efficiency, and long-term durability. If your engine isn't running as smoothly as it should, or you're experiencing power loss, a faulty knock sensor could be the culprit.. Why This Sensor Matters:. Prevents Costly Engine Damage - Detects knock early, allowing the ECM to adjust timing and protect internal components.. OEM Precision Fit - Designed specifically for MerCruiser V-6 and V-8 MPI engines with ECM 555, ensuring accurate readings and easy installation.. Built for Harsh Conditions - Engineered to withstand the demanding mari