Knock Sensor Mercruiser 805544T 

Knock Sensor
Replaces: Mercruiser 805544T / Volvo 3854512
Fits: MCM/MIE GM V8 454, 502, 540, 572

These Mallory Marine ignition knock sensors maximize your engine's performance--regardless of fuel quality! The knock sensors hear various knock frequencies under many operating conditions to detect shifts and provide an accurate signal to your engine control module. The sensors meet or exceed OE requirements and reduce potential damage to your internal engine components