{"product_id":"knock-sensor-fits-mercury-mercruiser-omc-volvo-penta-5-0-5-7-replaces-806612t-3850357-r020027-18-7677","title":"Knock Sensor – Fits Mercury MerCruiser OMC Volvo Penta 5.0 5.7 (Replaces 806612T, 3850357, R020027, 18-7677)","description":"\u003cstyle\u003e\n  .ss-table-wrap { overflow-x:auto; -webkit-overflow-scrolling:touch; }\n  table.ss-table { width:100%; border-collapse:collapse; min-width:640px; }\n  table.ss-table th, table.ss-table td {\n    padding:10px 12px; border:1px solid #e5e7eb; text-align:left; vertical-align:top;\n  }\n  table.ss-table th {\n    white-space:nowrap;\n    word-break:normal;\n    letter-spacing:normal;\n    font-weight:600;\n    background:#f8fafc;\n  }\n  @media (max-width:480px){\n    table.ss-table th, table.ss-table td { padding:8px 10px; font-size:14px; }\n  }\n\u003c\/style\u003e\n\n\u003ch2\u003eProduct Details\u003c\/h2\u003e\n\n\u003cp\u003eThis \u003cstrong\u003eKnock Sensor\u003c\/strong\u003e is designed for GM small block V8 marine engines, including the 305 (5.0L), 350 (5.7L), and 377 (6.2L) powerplants found in Mercury MerCruiser, OMC, Volvo Penta, PCM, Marine Power, and Crusader applications. The sensor installs into the water port in the middle of the engine block, just above the oil pan, where it monitors combustion events to detect pre-ignition or detonation.\u003c\/p\u003e\n\n\u003cp\u003eThis aftermarket unit replaces Mercury MerCruiser 806612T, OMC\/Volvo Penta 3850357, Crusader R020027, and Sierra 18-7677.\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003eDetects pre-ignition and detonation, signaling the ECM to retard timing and prevent piston or valve damage\u003c\/li\u003e\n  \u003cli\u003eMounts in the block water port above the oil pan on GM small block engines\u003c\/li\u003e\n  \u003cli\u003eDirect fit for multiple marine brands using GM V8 platforms\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003ePart Number Matrix\u003c\/h2\u003e\n\n\u003cp\u003eUse this matrix to confirm equivalent references across OEM and aftermarket.\u003c\/p\u003e\n\n\u003cdiv class=\"ss-table-wrap\"\u003e\n  \u003ctable class=\"ss-table\" aria-label=\"Part Number Matrix\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth\u003eBrand\u003c\/th\u003e\n        \u003cth\u003ePart Number\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury MerCruiser\u003c\/td\u003e\n        \u003ctd\u003e806612T\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eVolvo Penta\u003c\/td\u003e\n        \u003ctd\u003e3850357\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eCrusader\u003c\/td\u003e\n        \u003ctd\u003eR020027\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eSierra\u003c\/td\u003e\n        \u003ctd\u003e18-7677\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eEngine \u0026amp; Model Compatibility\u003c\/h2\u003e\n\n\u003cp\u003eConfirm your engine model\/year in the table below.\u003c\/p\u003e\n\n\u003cdiv class=\"ss-table-wrap\"\u003e\n  \u003ctable class=\"ss-table\" aria-label=\"Engine \u0026amp; Model Compatibility\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth\u003eBrand\u003c\/th\u003e\n        \u003cth\u003eEngine Model\u003c\/th\u003e\n        \u003cth\u003eNotes\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury MerCruiser\u003c\/td\u003e\n        \u003ctd\u003e5.0L, 5.7L (GM Small Block V8)\u003c\/td\u003e\n        \u003ctd\u003e305, 350 engines\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eOMC\u003c\/td\u003e\n        \u003ctd\u003e5.0L, 5.7L (GM Small Block V8)\u003c\/td\u003e\n        \u003ctd\u003e305, 350 engines\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eVolvo Penta\u003c\/td\u003e\n        \u003ctd\u003e5.0L, 5.7L (GM Small Block V8)\u003c\/td\u003e\n        \u003ctd\u003e305, 350 engines\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003ePCM\u003c\/td\u003e\n        \u003ctd\u003eGM Small Block V8\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMarine Power\u003c\/td\u003e\n        \u003ctd\u003eGM Small Block V8\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eCrusader\u003c\/td\u003e\n        \u003ctd\u003eGM Small Block V8\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eTechnical Specs\u003c\/h2\u003e\n\n\u003cdl\u003e\n  \u003cdt\u003eEngine Type\u003c\/dt\u003e\n  \u003cdd\u003eGM Small Block V8 (305, 350, 377)\u003c\/dd\u003e\n  \u003cdt\u003eApplication\u003c\/dt\u003e\n  \u003cdd\u003eMarine (MerCruiser, OMC, Volvo Penta, PCM, Marine Power, Crusader)\u003c\/dd\u003e\n  \u003cdt\u003eFunction\u003c\/dt\u003e\n  \u003cdd\u003eDetects pre-ignition\/detonation; sends signal to ECM to retard timing\u003c\/dd\u003e\n  \u003cdt\u003eMounting Location\u003c\/dt\u003e\n  \u003cdd\u003eWater port in engine block, above oil pan\u003c\/dd\u003e\n\u003c\/dl\u003e\n\n\u003ch2\u003eWhat's in the Box\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003e1 × Knock Sensor\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eInstallation Notes\u003c\/h2\u003e\n\n\u003col\u003e\n  \u003cli\u003eDisconnect the battery and ensure the engine is cool before beginning work.\u003c\/li\u003e\n  \u003cli\u003eLocate the water port on the side of the engine block, just above the oil pan.\u003c\/li\u003e\n  \u003cli\u003eDisconnect the electrical connector from the old knock sensor.\u003c\/li\u003e\n  \u003cli\u003eRemove the old sensor using the appropriate socket or wrench.\u003c\/li\u003e\n  \u003cli\u003eInspect the mounting threads in the block for damage or debris; clean if necessary.\u003c\/li\u003e\n  \u003cli\u003eInstall the new knock sensor hand-tight, then torque to manufacturer specification (typically 12–18 ft-lbs; consult your engine manual).\u003c\/li\u003e\n  \u003cli\u003eReconnect the electrical connector until it clicks into place.\u003c\/li\u003e\n  \u003cli\u003eReconnect the battery and start the engine to verify proper operation and absence of fault codes.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch2\u003eTroubleshooting \u0026amp; FAQ\u003c\/h2\u003e\n\n\u003cdetails\u003e\n  \u003csummary\u003eWhat are the symptoms of a failing knock sensor?\u003c\/summary\u003e\n  \u003cp\u003eCommon signs include engine pinging or knocking under load, reduced power, poor fuel economy, and illuminated check-engine light with knock sensor fault codes. If the ECM cannot detect detonation, it may run overly conservative timing maps or allow damaging knock to occur.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003cdetails\u003e\n  \u003csummary\u003eWhere exactly does this sensor install?\u003c\/summary\u003e\n  \u003cp\u003eThe knock sensor threads into a water port on the side of the engine block, positioned in the middle of the block just above the oil pan on GM small block V8 engines. This central location allows it to monitor vibrations across all cylinders.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003cdetails\u003e\n  \u003csummary\u003eCan I test my old knock sensor before replacing it?\u003c\/summary\u003e\n  \u003cp\u003eYes. Use a multimeter to measure resistance across the sensor terminals (typical range 93–107 kΩ at room temperature, but verify your engine's spec). You can also tap the sensor lightly with a small wrench while monitoring voltage output on a scan tool; a healthy sensor will produce a brief voltage spike.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003cdetails\u003e\n  \u003csummary\u003eWill this sensor work on freshwater and saltwater engines?\u003c\/summary\u003e\n  \u003cp\u003eYes. The sensor is compatible with both freshwater and saltwater marine applications. Ensure all electrical connections are sealed and protected from corrosion, especially in saltwater environments.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003cdetails\u003e\n  \u003csummary\u003eWhat torque specification should I use?\u003c\/summary\u003e\n  \u003cp\u003eTypical torque is 12–18 ft-lbs, but always consult your engine service manual for the exact value. Over-tightening can damage the sensor or block threads; under-tightening may cause poor thermal contact or leaks.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003cdetails\u003e\n  \u003csummary\u003eHow often should the knock sensor be replaced?\u003c\/summary\u003e\n  \u003cp\u003eKnock sensors do not have a fixed service interval and are typically replaced only when they fail or produce fault codes. Regular engine maintenance and using quality fuel can extend sensor life.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003cdetails\u003e\n  \u003csummary\u003eOEM vs. Aftermarket?\u003c\/summary\u003e\n  \u003cp\u003eThis listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003cdetails\u003e\n  \u003csummary\u003eShipping speed \u0026amp; cost\u003c\/summary\u003e\n  \u003cp\u003eWe ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003cdetails\u003e\n  \u003csummary\u003eWarranty \u0026amp; returns\u003c\/summary\u003e\n  \u003cp\u003eCovered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused \u0026amp; in original condition). See our policy page or reach out for instructions.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003ch2\u003eSafety \u0026amp; Important Info\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003eVerify images\/specifications against your original part. If anything differs—even if your model appears compatible—do not purchase.\u003c\/li\u003e\n  \u003cli\u003eThis is an aftermarket replacement, not an OEM component.\u003c\/li\u003e\n  \u003cli\u003eProfessional installation is recommended for safety and performance.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eAbout Sea Sierra\u003c\/h2\u003e\n\n\u003cul\u003e\n  \u003cli\u003ePro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.\u003c\/li\u003e\n  \u003cli\u003eFast Global Fulfillment — Free standard delivery to most regions in 5–15 days.\u003c\/li\u003e\n  \u003cli\u003eManufacturer-Direct Value — Fair pricing without compromising on materials or QC.\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"SeaSierra","offers":[{"title":"Default Title","offer_id":51025604149563,"sku":"21SR010","price":18.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0826\/8673\/8747\/files\/Ud03d9381d59c4522b4406d07875eb80fe.webp?v=1772931241","url":"https:\/\/seasierra.com\/products\/knock-sensor-fits-mercury-mercruiser-omc-volvo-penta-5-0-5-7-replaces-806612t-3850357-r020027-18-7677","provider":"SeaSierra","version":"1.0","type":"link"}