{"product_id":"lower-unit-seal-kit-fits-johnson-evinrude-18-25-hp-replaces-18-2684-87606-9-74105","title":"Lower Unit Seal Kit – Fits Johnson\/Evinrude 18-25 HP (Replaces 18-2684, 87606, 9-74105)","description":"\u003csection\u003e\n\u003ch2\u003eProduct Details\u003c\/h2\u003e\n\u003cp\u003eThis \u003cstrong\u003eLower Unit Seal Kit – Fits Johnson\/Evinrude 18-25 HP\u003c\/strong\u003e provides all necessary seals to service the lower unit gearcase on Johnson\/Evinrude outboard motors. It is designed for 18 HP (1958–1973), 20 HP (1966–1973, 1979), and 25 HP (1969–1978) 2-Stroke models. The kit also fits select 6 HP outboards from 1967 (\"S\" suffix) and 1968 (\"C\" suffix).\u003c\/p\u003e\n\u003cp\u003eThis kit serves as a direct replacement for Sierra 18-2684, GLM 87606, and Mallory 9-74105.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eReplaces all essential OEM lower unit gearcase seals for a complete service.\u003c\/li\u003e\n\u003cli\u003eSuitable for both DIY and professional installation.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/section\u003e\n\u003csection\u003e\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\u003c!-- 🔧 Table Styles (include only once per page) --\u003e\n\u003cstyle\u003e\n  \/* Outer container allows horizontal scrolling (with iOS momentum) *\/\n  .ss-table-wrap { overflow-x:auto; -webkit-overflow-scrolling:touch; }\n\n  \/* Base table styles *\/\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\n  \/* Key: prevent wrapping, word breaks, and vertical text in headers *\/\n  table.ss-table th {\n    white-space:nowrap;       \/* Do not wrap *\/\n    word-break:normal;        \/* Don’t break words *\/\n    letter-spacing:normal;    \/* Prevent theme styles from stretching letters *\/\n    font-weight:600;\n    background:#f8fafc;\n  }\n\n  \/* Small screen optimization *\/\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\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\u003eSierra\u003c\/td\u003e\n        \u003ctd\u003e18-2684\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eGLM\u003c\/td\u003e\n        \u003ctd\u003e87606\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMallory\u003c\/td\u003e\n        \u003ctd\u003e9-74105\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/div\u003e\n\u003c\/section\u003e\n\u003csection\u003e\n\u003ch2\u003eEngine \u0026amp; Model Compatibility\u003c\/h2\u003e\n\u003cp\u003eConfirm your engine model\/year in the table below.\u003c\/p\u003e\n\u003cp\u003eFor Johnson\/Evinrude applications, pay close attention to the model year and any specific suffixes noted, as fitment can vary.\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\u003eModel\u003c\/th\u003e\n        \u003cth\u003eRated HP\u003c\/th\u003e\n        \u003cth\u003eStroke\u003c\/th\u003e\n        \u003cth\u003eYears\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\u003eJohnson\/Evinrude\u003c\/td\u003e\n        \u003ctd\u003eOutboard\u003c\/td\u003e\n        \u003ctd\u003e6\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e1967\u003c\/td\u003e\n        \u003ctd\u003e\"S\" suffix only; Limited application\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eJohnson\/Evinrude\u003c\/td\u003e\n        \u003ctd\u003eOutboard\u003c\/td\u003e\n        \u003ctd\u003e6\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e1968\u003c\/td\u003e\n        \u003ctd\u003e\"C\" suffix only; Limited application\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eJohnson\/Evinrude\u003c\/td\u003e\n        \u003ctd\u003eOutboard\u003c\/td\u003e\n        \u003ctd\u003e18\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e1958–1973\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eJohnson\/Evinrude\u003c\/td\u003e\n        \u003ctd\u003eOutboard\u003c\/td\u003e\n        \u003ctd\u003e20\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e1966–1973, 1979\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eJohnson\/Evinrude\u003c\/td\u003e\n        \u003ctd\u003eOutboard\u003c\/td\u003e\n        \u003ctd\u003e25\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e1969–1978\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\u003c\/section\u003e\n\u003csection\u003e\n\u003ch2\u003eTechnical Specs\u003c\/h2\u003e\n\u003cdl\u003e\n  \u003cdt\u003eProduct Type\u003c\/dt\u003e\n\u003cdd\u003eLower Unit Seal Kit\u003c\/dd\u003e\n  \u003cdt\u003eInstallation\u003c\/dt\u003e\n\u003cdd\u003eDIY\/Professional\u003c\/dd\u003e\n  \u003cdt\u003eWeight\u003c\/dt\u003e\n\u003cdd\u003e0.05 lbs (0.023 kg)\u003c\/dd\u003e\n  \u003cdt\u003eOther Technical Attributes\u003c\/dt\u003e\n\u003cdd\u003eReplaces OEM lower unit gearcase seals\u003c\/dd\u003e\n\u003c\/dl\u003e\n\u003c\/section\u003e\n\u003csection\u003e\n\u003ch2\u003eWhat’s in the Box\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e1 x Shift Rod Gasket (304764\/18-0882)\u003c\/li\u003e\n  \u003cli\u003e1 x Oil Seal (0321787\/18-2031)\u003c\/li\u003e\n  \u003cli\u003e\u003cspan style=\"color:#d0021b;\"\u003e2 x Oil Seal (0321788\/18-2032)\u003c\/span\u003e\u003c\/li\u003e\n  \u003cli\u003e1 x Seal (309044\/18-2534)\u003c\/li\u003e\n  \u003cli\u003e\u003cspan style=\"color:#d0021b;\"\u003e2 x Drain\/Fill Plug Washer (311598\/18-4248)\u003c\/span\u003e\u003c\/li\u003e\n  \u003cli\u003e1 x O-Ring (301877\/18-7100)\u003c\/li\u003e\n  \u003cli\u003e1 x O-Ring (307853\/18-7120)\u003c\/li\u003e\n  \u003cli\u003e1 x O-Ring (321921\/18-7411)\u003c\/li\u003e\n  \u003cli\u003e1 x O-Ring (302493\/18-7112)\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/section\u003e\n\u003csection\u003e\n\u003ch2\u003eInstallation Notes\u003c\/h2\u003e\n\u003col\u003e\n    \u003cli\u003ePlace a drain pan under the lower unit and remove the drain\/fill screws to empty the gear lube.\u003c\/li\u003e\n    \u003cli\u003eRemove the propeller and disconnect the shift linkage. Unbolt and carefully lower the gearcase from the engine.\u003c\/li\u003e\n    \u003cli\u003eDisassemble the gearcase components, including the propeller shaft housing and driveshaft bearing carrier, exposing the old seals.\u003c\/li\u003e\n    \u003cli\u003eCarefully remove all old seals, O-rings, and gaskets, taking note of their orientation. Clean the sealing surfaces thoroughly.\u003c\/li\u003e\n    \u003cli\u003eLubricate the new seals with marine grease and press them into place using an appropriate seal driver or socket. Ensure they are seated correctly.\u003c\/li\u003e\n    \u003cli\u003eInstall the new gaskets and O-rings, reassembling the gearcase components in reverse order.\u003c\/li\u003e\n    \u003cli\u003eRe-install the lower unit onto the engine, reconnect the shift linkage, and torque all bolts to the manufacturer's specification.\u003c\/li\u003e\n    \u003cli\u003eRefill the gearcase with fresh lower unit lube from the bottom fill hole until it seeps out the top vent hole. Re-install both screws with new washers.\u003c\/li\u003e\n    \u003cli\u003eAfter running the engine, check for any signs of water intrusion or oil leaks.\u003c\/li\u003e\n\u003c\/ol\u003e\n\u003c\/section\u003e\n\u003csection\u003e\n\u003ch2\u003eTroubleshooting \u0026amp; FAQ\u003c\/h2\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWhat are the signs my lower unit seals are failing?\u003c\/summary\u003e\n  \u003cp\u003eThe most common sign of a failed seal is milky, creamy, or cloudy gear lube, which indicates water has entered the gearcase. You may also notice oil leaking from around the propeller shaft or dripping from the skeg.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eHow can I confirm this kit fits my engine?\u003c\/summary\u003e\n  \u003cp\u003ePlease check the \"Engine \u0026amp; Model Compatibility\" table. For the 6 HP models, it is essential to match both the year and the specific model suffix (\"S\" for 1967, \"C\" for 1968), as fitment is limited.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eHow often should I replace lower unit seals?\u003c\/summary\u003e\n  \u003cp\u003eIt is recommended to inspect your gear lube annually for water intrusion. Seals should be replaced every 3-5 years as preventative maintenance, or immediately if you detect a leak or water in the oil.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eDoes this kit include every seal in the lower unit?\u003c\/summary\u003e\n  \u003cp\u003eThis kit contains the most commonly replaced seals for a standard lower unit service, as detailed in the \"What’s in the Box\" section. For a complete overhaul, you may need additional parts. Always compare the included parts with your unit's requirements.\u003c\/p\u003e\n\u003c\/details\u003e\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\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\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\u003c\/section\u003e\n\u003csection\u003e\n\u003ch2\u003eSafety \u0026amp; Important Info\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eVerify images\/specifications vs 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\u003c\/section\u003e\n\u003csection\u003e\n\u003ch2\u003eAbout Sea Sierra\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePro-Grade Standards\u003c\/strong\u003e — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFast Global Fulfillment\u003c\/strong\u003e — Free standard delivery to most regions in 5–15 days.\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eManufacturer-Direct Value\u003c\/strong\u003e — Fair pricing without compromising on materials or QC.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/section\u003e","brand":"SeaSierra","offers":[{"title":"Default Title","offer_id":50723788652859,"sku":"SS-24OSK707","price":28.99,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0826\/8673\/8747\/files\/SS-24OSK707.png?v=1763031792","url":"https:\/\/seasierra.com\/products\/lower-unit-seal-kit-fits-johnson-evinrude-18-25-hp-replaces-18-2684-87606-9-74105","provider":"SeaSierra","version":"1.0","type":"link"}