{"product_id":"knock-sensor-assembly-fits-volvo-penta-omc-cobra-sterndrives-replaces-3854905-18-7679","title":"Knock Sensor Assembly – Fits Volvo Penta OMC Cobra Sterndrives (Replaces 3854905, 18-7679)","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\u003cp\u003eThis \u003cstrong\u003eKnock Sensor Assembly\u003c\/strong\u003e is designed for Volvo Penta and OMC Cobra sterndrive marine engines. It provides accurate engine knock detection to protect your engine from detonation damage and ensure optimal performance across a wide range of operating conditions.\u003c\/p\u003e\n\u003cp\u003eThis aftermarket assembly directly replaces Volvo Penta part number 3854905, OMC Cobra 3854905, Sierra 18-7679, and Mallory 9-33504.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003ePrecision knock detection for engine protection\u003c\/li\u003e\n  \u003cli\u003eBuilt to withstand marine environments\u003c\/li\u003e\n  \u003cli\u003eDirect-fit replacement for OEM sensors\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003ePart Number Matrix\u003c\/h2\u003e\n\u003cp\u003eUse this matrix to confirm equivalent references across OEM and aftermarket.\u003c\/p\u003e\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\u003eVolvo Penta\u003c\/td\u003e\n        \u003ctd\u003e3854905\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eOMC Cobra\u003c\/td\u003e\n        \u003ctd\u003e3854905\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eSierra\u003c\/td\u003e\n        \u003ctd\u003e18-7679\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMallory\u003c\/td\u003e\n        \u003ctd\u003e9-33504\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\u003cp\u003eConfirm your engine model\/year in the table below.\u003c\/p\u003e\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 Type\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\u003eVolvo Penta\u003c\/td\u003e\n        \u003ctd\u003eSterndrive Marine Engines\u003c\/td\u003e\n        \u003ctd\u003eStern out drive applications\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eOMC\u003c\/td\u003e\n        \u003ctd\u003eCobra Sterndrive Marine Engines\u003c\/td\u003e\n        \u003ctd\u003eAll Cobra sterndrive models\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\u003cdl\u003e\n  \u003cdt\u003eType\u003c\/dt\u003e\n  \u003cdd\u003eMarine Knock Sensor\u003c\/dd\u003e\n  \u003cdt\u003eEngine Type\u003c\/dt\u003e\n  \u003cdd\u003eOMC \/ VOLVO PENTA Sterndrive\u003c\/dd\u003e\n  \u003cdt\u003eApplication\u003c\/dt\u003e\n  \u003cdd\u003eSterndrive marine engines\u003c\/dd\u003e\n  \u003cdt\u003eOEM Reference\u003c\/dt\u003e\n  \u003cdd\u003e3854905\u003c\/dd\u003e\n\u003c\/dl\u003e\n\n\u003ch2\u003eWhat's in the Box\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\u003cstrong\u003e1 × Marine Knock Sensor\u003c\/strong\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eInstallation Notes\u003c\/h2\u003e\n\u003col\u003e\n  \u003cli\u003eDisconnect the battery negative terminal before beginning work.\u003c\/li\u003e\n  \u003cli\u003eLocate the original knock sensor on your engine block, typically mounted on the intake manifold or block side.\u003c\/li\u003e\n  \u003cli\u003eDisconnect the electrical connector from the old sensor.\u003c\/li\u003e\n  \u003cli\u003eRemove the mounting bolt and carefully extract the old knock sensor.\u003c\/li\u003e\n  \u003cli\u003eClean the mounting surface to ensure proper contact and sealing.\u003c\/li\u003e\n  \u003cli\u003eInstall the new knock sensor hand-tight, then torque to manufacturer specifications (typically 12–18 ft-lbs).\u003c\/li\u003e\n  \u003cli\u003eReconnect the electrical connector until it clicks into place.\u003c\/li\u003e\n  \u003cli\u003eReconnect the battery and clear any stored engine codes if necessary.\u003c\/li\u003e\n  \u003cli\u003eStart the engine and verify normal operation with no warning lights.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch2\u003eTroubleshooting \u0026amp; FAQ\u003c\/h2\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eHow do I know if my knock sensor is failing?\u003c\/summary\u003e\n  \u003cp\u003eCommon symptoms include engine pinging or knocking under load, reduced fuel economy, poor acceleration, check engine light illumination, and stored diagnostic trouble codes related to knock sensor circuit or performance.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWill this fit my Volvo Penta sterndrive?\u003c\/summary\u003e\n  \u003cp\u003eThis sensor fits Volvo Penta sterndrive engines that originally used part number 3854905. Verify your engine's part number against the compatibility table to confirm fitment before ordering.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eCan I install this myself or do I need a mechanic?\u003c\/summary\u003e\n  \u003cp\u003eInstallation is straightforward for those with basic mechanical skills and proper tools. However, proper torque specifications and electrical connector handling are critical. Professional installation is recommended if you're unfamiliar with marine engine components.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWhat torque specification should I use?\u003c\/summary\u003e\n  \u003cp\u003eTypical torque for knock sensors is 12–18 ft-lbs, but always consult your engine's service manual for exact specifications. Over-tightening can damage the sensor or mounting threads.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eHow often should the knock sensor be replaced?\u003c\/summary\u003e\n  \u003cp\u003eKnock sensors typically last many years under normal conditions. Replace when you experience knock-related engine codes, audible engine knock, or performance issues. Routine replacement is not usually required unless failure symptoms appear.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWhat's the difference between this and the OEM sensor?\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\u003cdetails\u003e\n  \u003csummary\u003eHow fast will this ship and what does it 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\u003cdetails\u003e\n  \u003csummary\u003eWhat warranty and return options are available?\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\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\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":51025809310011,"sku":"23SE185","price":30.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0826\/8673\/8747\/files\/12_eae8e934-51dd-4c94-bbce-6e93c6556391.jpg?v=1772959414","url":"https:\/\/seasierra.com\/products\/knock-sensor-assembly-fits-volvo-penta-omc-cobra-sterndrives-replaces-3854905-18-7679","provider":"SeaSierra","version":"1.0","type":"link"}