{"product_id":"lower-unit-seal-kit-fits-mercury-mariner-9-9-25hp-outboards-replaces-26-85090a2-18-2624","title":"Lower Unit Seal Kit – Fits Mercury\/Mariner 9.9-25HP Outboards (Replaces 26-85090A2, 18-2624)","description":"\u003csection\u003e\n\u003ch2\u003eProduct Details\u003c\/h2\u003e\n\u003cp\u003eThis Lower Unit Seal Kit provides the essential components to service and reseal the lower gearcase on Mercury\/Mariner 9.9–25HP outboard engines. Designed for both 2-Stroke and 4-Stroke models, this kit helps prevent water intrusion and gear lube leaks, restoring the integrity of your outboard's lower unit.\u003c\/p\u003e\n\u003cp\u003eIt serves as a direct aftermarket replacement for Mercury OEM part 26-85090A2 and interchanges with Sierra 18-2624 and SeaSierra 18-2624.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eEngineered for direct replacement of the original seals.\u003c\/li\u003e\n\u003cli\u003eIncludes a comprehensive set of seals, O-rings, and gaskets for a complete service.\u003c\/li\u003e\n\u003cli\u003eConstructed from high-quality, reinforced rubber and gasket materials for durability and a reliable seal.\u003c\/li\u003e\n\u003c\/ul\u003e\n\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\n\u003ch2\u003ePart Number Matrix\u003c\/h2\u003e\n\u003cp\u003eUse this matrix to confirm equivalent references across OEM and aftermarket providers.\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\u003eMercury\u003c\/td\u003e\n        \u003ctd\u003e26-85090A2\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eSierra\u003c\/td\u003e\n        \u003ctd\u003e18-2624\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eSeaSierra\u003c\/td\u003e\n        \u003ctd\u003e18-2624\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 and horsepower in the table below. Matching the OEM part number is the most reliable way to ensure correct fitment.\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\u003eOEM Part No.\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\u003c\/td\u003e\n        \u003ctd\u003eOutboard\u003c\/td\u003e\n        \u003ctd\u003e9.9\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke \u0026amp; 4-Stroke\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n        \u003ctd\u003e26-85090A2\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\u003c\/td\u003e\n        \u003ctd\u003eOutboard\u003c\/td\u003e\n        \u003ctd\u003e15\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke \u0026amp; 4-Stroke\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n        \u003ctd\u003e26-85090A2\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\u003c\/td\u003e\n        \u003ctd\u003eOutboard\u003c\/td\u003e\n        \u003ctd\u003e20\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n        \u003ctd\u003e26-85090A2\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMercury\u003c\/td\u003e\n        \u003ctd\u003eOutboard\u003c\/td\u003e\n        \u003ctd\u003e25\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n        \u003ctd\u003e26-85090A2\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMariner\u003c\/td\u003e\n        \u003ctd\u003eOutboard\u003c\/td\u003e\n        \u003ctd\u003e9.9\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke \u0026amp; 4-Stroke\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n        \u003ctd\u003e26-85090A2\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMariner\u003c\/td\u003e\n        \u003ctd\u003eOutboard\u003c\/td\u003e\n        \u003ctd\u003e15\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke \u0026amp; 4-Stroke\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n        \u003ctd\u003e26-85090A2\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMariner\u003c\/td\u003e\n        \u003ctd\u003eOutboard\u003c\/td\u003e\n        \u003ctd\u003e20\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n        \u003ctd\u003e26-85090A2\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eMariner\u003c\/td\u003e\n        \u003ctd\u003eOutboard\u003c\/td\u003e\n        \u003ctd\u003e25\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n        \u003ctd\u003e26-85090A2\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\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\u003eDirect replacement\u003c\/dd\u003e\n  \u003cdt\u003eHousing Material\u003c\/dt\u003e\n\u003cdd\u003eReinforced rubber seals and gaskets\u003c\/dd\u003e\n  \u003cdt\u003eHousing Color\u003c\/dt\u003e\n\u003cdd\u003eBlack\u003c\/dd\u003e\n  \u003cdt\u003eWeight\u003c\/dt\u003e\n\u003cdd\u003e50g (0.11 lb)\u003c\/dd\u003e\n\u003c\/dl\u003e\n\n\u003ch2\u003eWhat’s in the Box\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e1 x Lower Unit Seal Kit (Replaces 26-85090A2 \/ 18-2624)\u003c\/li\u003e\n  \u003cli\u003eAssorted seals, gaskets, and O-rings for complete lower unit service\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eInstallation Notes\u003c\/h2\u003e\n\u003col\u003e\n  \u003cli\u003eDrain the gearcase oil completely from the lower unit.\u003c\/li\u003e\n  \u003cli\u003eRemove the propeller, thrust washer, and any related hardware.\u003c\/li\u003e\n  \u003cli\u003eUnbolt and carefully separate the lower unit from the outboard's midsection.\u003c\/li\u003e\n  \u003cli\u003eDisassemble the water pump assembly to gain access to the driveshaft seals.\u003c\/li\u003e\n  \u003cli\u003eDisassemble the propeller shaft bearing carrier to access the propeller shaft seals.\u003c\/li\u003e\n  \u003cli\u003eCarefully remove all old seals, o-rings, and gaskets. Using a seal puller is recommended to prevent damage to the housing.\u003c\/li\u003e\n  \u003cli\u003eThoroughly clean all sealing surfaces, removing any old adhesive or sealant.\u003c\/li\u003e\n  \u003cli\u003eLightly lubricate new seals and O-rings with marine grease before installation.\u003c\/li\u003e\n  \u003cli\u003eInstall the new seals squarely into their bores using a suitable seal driver or socket.\u003c\/li\u003e\n  \u003cli\u003eReassemble all components in the reverse order of disassembly, ensuring bolts are torqued to manufacturer specifications.\u003c\/li\u003e\n  \u003cli\u003eInstall a new drain screw washer and refill the gearcase with the correct type and amount of fresh gear lube.\u003c\/li\u003e\n  \u003cli\u003eSubmerge the lower unit and check for any signs of water intrusion or oil leaks before operating.\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 this seal kit fits my specific engine year?\u003c\/summary\u003e\n  \u003cp\u003eThis kit is designed for a wide range of Mercury\/Mariner 9.9HP, 15HP, 20HP, and 25HP outboards. Since specific year ranges are not always provided by manufacturers, the best method is to match the OEM part number (26-85090A2) from your engine's service manual with the one this kit replaces.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWhat are the signs that my lower unit seals are failing?\u003c\/summary\u003e\n  \u003cp\u003eCommon signs include a milky or foamy appearance in your gear lube (indicating water has mixed with the oil) or a visible oil leak around the propeller shaft or driveshaft housing. Fishing line wrapped around the prop shaft is a frequent cause of seal failure.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eHow often should lower unit seals be replaced?\u003c\/summary\u003e\n  \u003cp\u003eThere is no fixed replacement interval. It is best practice to inspect for leaks at every service. We recommend proactively replacing the seals whenever the lower unit is disassembled for other maintenance (like a water pump impeller change) or immediately if you detect a leak.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eIs any special tool required for installation?\u003c\/summary\u003e\n  \u003cp\u003eWhile basic hand tools are sufficient for disassembly, using a dedicated seal puller for removal and a proper seal driver (or a socket of the correct diameter) for installation is highly recommended to avoid damaging the new seals or the housing surfaces.\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\n\u003ch2\u003eSafety \u0026amp; Important Info\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003eVerify images and 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 component, not an OEM part.\u003c\/li\u003e\n  \u003cli\u003eProfessional installation is recommended for safety and optimal performance.\u003c\/li\u003e\n\u003c\/ul\u003e\n\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.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eManufacturer-Direct Value\u003c\/strong\u003e — Fair pricing without compromising on materials or quality control.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/section\u003e","brand":"SeaSierra","offers":[{"title":"Default Title","offer_id":50718272422203,"sku":"24PSK629R","price":64.5,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0826\/8673\/8747\/files\/24PSK629R.png?v=1762958779","url":"https:\/\/seasierra.com\/products\/lower-unit-seal-kit-fits-mercury-mariner-9-9-25hp-outboards-replaces-26-85090a2-18-2624","provider":"SeaSierra","version":"1.0","type":"link"}