{"product_id":"sierra-heavy-duty-u-joint-18-2104","title":"Sierra Heavy-Duty U-Joint 18-2104 | MerCruiser \/ OMC \/ Volvo Penta","description":"\u003ch2\u003eSierra Heavy-Duty U-Joint 18-2104\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003ePart Number:\u003c\/strong\u003e 18-2104 (Sierra)  |  \u003cstrong\u003eUPC:\u003c\/strong\u003e 030999310293\u003c\/p\u003e\n\u003cp\u003eThe Sierra 18-2104 is a heavy-duty, greasable Rockwell-style universal joint for selected MerCruiser, OMC Cobra, and Volvo Penta AQ-series sterndrive drivelines. It transmits torque between the engine coupler and the drive while allowing angular movement through the transom. The kit includes both a straight grease fitting and a 90° grease fitting for flexible service access, plus retaining clips.\u003c\/p\u003e\n\n\u003ch3\u003eSpecifications\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eConstruction:\u003c\/strong\u003e Rockwell style, heavy-duty steel\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eGreasable:\u003c\/strong\u003e Yes\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIncludes:\u003c\/strong\u003e Straight grease fitting, 90° grease fitting, retaining clips\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eCompatible Applications\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eMerCruiser\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eMerCruiser #1\u003c\/li\u003e\n\u003cli\u003eMR \/ Early Alpha One  (Serial: 1684188 through B418818)\u003c\/li\u003e\n\u003cli\u003eTR\u003c\/li\u003e\n\u003cli\u003eTRS\u003c\/li\u003e\n\u003cli\u003eII SSM\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003eOMC\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eOMC Cobra  —  approx. 1986–1989\u003c\/li\u003e\n\u003cli\u003eOEM references: 912214, 915716\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003eVolvo Penta\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eAQ200\u003c\/li\u003e\n\u003cli\u003eAQ250\u003c\/li\u003e\n\u003cli\u003eAQ270\u003c\/li\u003e\n\u003cli\u003eAQ280\u003c\/li\u003e\n\u003cli\u003eAQ290\u003c\/li\u003e\n\u003cli\u003eOEM references: 853255, 897707\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eFitment Notice\u003c\/h3\u003e\n\u003cp\u003eLater Alpha One, OMC\/Volvo, SX, and DP-S drivetrains can use different universal joints. Confirm before ordering:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eDrive model and generation\u003c\/li\u003e\n\u003cli\u003eDrive serial number\u003c\/li\u003e\n\u003cli\u003eExisting U-joint part number\u003c\/li\u003e\n\u003cli\u003eRetaining-clip style\u003c\/li\u003e\n\u003cli\u003eGrease-fitting access requirement\u003c\/li\u003e\n\u003cli\u003eYoke condition\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eOEM \u0026amp; Cross-Reference Part Numbers\u003c\/h3\u003e\n\u003cp\u003e\u003cstrong\u003eMercury \/ MerCruiser\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e36312\u003c\/li\u003e\n\u003cli\u003e41431\u003c\/li\u003e\n\u003cli\u003e58749\u003c\/li\u003e\n\u003cli\u003e75832\u003c\/li\u003e\n\u003cli\u003e758321\u003c\/li\u003e\n\u003cli\u003e75832A1\u003c\/li\u003e\n\u003cli\u003e75832A2\u003c\/li\u003e\n\u003cli\u003e75832A3\u003c\/li\u003e\n\u003cli\u003e75832T\u003c\/li\u003e\n\u003cli\u003e75832T1\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003eOMC\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e912214\u003c\/li\u003e\n\u003cli\u003e915716\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003eVolvo Penta\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e853255\u003c\/li\u003e\n\u003cli\u003e897707\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003eAftermarket\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eMallory 9-72404\u003c\/li\u003e\n\u003cli\u003eGLM 28020\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhen to Replace the U-Joint\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003ePlay or looseness felt in the cross bearing\u003c\/li\u003e\n\u003cli\u003eNeedle bearings feel rough or bind during rotation\u003c\/li\u003e\n\u003cli\u003eRust, corrosion, or water contamination is visible\u003c\/li\u003e\n\u003cli\u003eGrease loss or bearing-cup damage is found\u003c\/li\u003e\n\u003cli\u003eClunking, vibration, or driveline shudder under load\u003c\/li\u003e\n\u003cli\u003eJoint operated with inadequate lubrication\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eInstallation Notes\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eRemove the sterndrive following the manufacturer's service procedure\u003c\/li\u003e\n\u003cli\u003eInspect both yokes for wear, distortion, or bore damage before installing the new joint\u003c\/li\u003e\n\u003cli\u003eSeat retaining clips fully into their grooves — a clip not fully seated is a common cause of joint failure\u003c\/li\u003e\n\u003cli\u003eChoose the straight or 90° grease fitting based on which provides better access in the installed position\u003c\/li\u003e\n\u003cli\u003eLubricate with the specified marine grease before and after installation\u003c\/li\u003e\n\u003cli\u003eWhile the drive is off, inspect the \u003ca href=\"\/products\/11077660180516\"\u003eU-joint bellows\u003c\/a\u003e, \u003ca href=\"\/products\/11077659688996\"\u003egimbal bearing\u003c\/a\u003e, and drive alignment\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eRelated Parts\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\u003ca href=\"\/products\/11077659918372\"\u003eSierra Heavy-Duty U-Joint (related SKU)\u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"\/products\/8131642490916\"\u003eU-Joint AP-1821\u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"\/products\/11077660180516\"\u003eU-Joint Bellows\u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"\/products\/11077660344356\"\u003eOMC U-Joint Bellows\u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"\/products\/8131374776356\"\u003eU-Joint Bellows — King Cobra\u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"\/products\/11077659688996\"\u003eSierra Gimbal Bearing 18-2100 | MerCruiser \/ OMC \/ Volvo Penta\u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"\/products\/11077659787300\"\u003eSierra 18-21006 Gimbal Bearing – MerCruiser Bravo \u0026amp; Gen II Sterndrive\u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"\/products\/8131402006564\"\u003eMercury Quicksilver Gimbal Housing Lock Nut 11-34087\u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"\/products\/11077660442660\"\u003eOMC Bellows Kit\u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"\/products\/11077660278820\"\u003eOMC Sterndrive \/ Cobra Exhaust Bellows\u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"\/products\/11119998435364\"\u003eSierra Cobra Outdrive Mounting Gasket Set (47-2613)\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eParts Desk Insights\u003c\/h3\u003e\n\u003cp\u003eThe Sierra 18-2104 is the correct heavy-duty U-joint for older MerCruiser drivelines through the early Alpha One era (serial through B418818) and for OMC Cobra and Volvo Penta AQ-series drives. The dual grease-fitting option — straight and 90° — makes in-service greasing practical even in tight transom areas.\u003c\/p\u003e\n\u003cp\u003eThe most common fitment error is assuming this joint fits all Alpha One drives. It covers the early Alpha One \/ MR serial range; later Alpha One, Bravo, and Alpha Gen II applications use different U-joints. Always cross-check the drive serial number and existing OEM joint number. On installation, the retaining clips are the single most important detail: a clip that isn’t fully seated in its groove will cause the bearing cup to walk out under load, leading to rapid joint failure and potential driveline damage.\u003c\/p\u003e","brand":"LNS","offers":[{"title":"Default Title","offer_id":51037541466148,"sku":"47-2104","price":121.09,"currency_code":"CAD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0743\/5799\/7604\/files\/88b2b0d7-bd8f-4bad-b650-c9db025b1ee8.png?v=1788809106","url":"https:\/\/marisolmarine.com\/products\/sierra-heavy-duty-u-joint-18-2104","provider":"Marisol Marine Company","version":"1.0","type":"link"}