{"product_id":"sei-yamaha-lower-unit-90-422-b25f-fits-yamaha-f250-outboards-with-25-driveshaft-replaces-6p2-45300-41-8d-43-8d","title":"SEI Yamaha Lower Unit 90-422-B25F – Fits Yamaha F250 Outboards with 25\" Driveshaft (Replaces 6P2-45300-41-8D\/43-8D)","description":"\u003csection\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\n\u003ch2\u003eProduct Details\u003c\/h2\u003e\n\u003cp\u003eThis is an aftermarket SEI Yamaha Lower Unit 90-422-B25F, engineered as a complete gearcase replacement for Yamaha 4-Stroke 250 HP F-series outboards (2005–2018) that require a 25\" driveshaft and a 2:1 gear ratio. It offers a reliable, cost-effective solution for restoring your engine's performance.\u003c\/p\u003e\n\u003cp\u003eIt serves as a direct interchange for Yamaha OEM part numbers 6P2-45300-41-8D, 6P2-45300-42-8D, and 6P2-45300-43-8D.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eDesigned for direct bolt-on installation.\u003c\/li\u003e\n  \u003cli\u003eComes complete with a pre-installed water pump.\u003c\/li\u003e\n  \u003cli\u003eConstructed from durable, marine-grade aluminum.\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\u003eSEI (Aftermarket)\u003c\/td\u003e\n        \u003ctd\u003e90-422-B25F\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha (OEM)\u003c\/td\u003e\n        \u003ctd\u003e6P2-45300-41-8D\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha (OEM)\u003c\/td\u003e\n        \u003ctd\u003e6P2-45300-42-8D\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha (OEM)\u003c\/td\u003e\n        \u003ctd\u003e6P2-45300-43-8D\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\u003cp\u003eThis lower unit is compatible with select Yamaha F250 and F225 series outboards. Please verify your specific model and year before ordering.\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\u003eYamaha\u003c\/td\u003e\n        \u003ctd\u003eF250XA\u003c\/td\u003e\n        \u003ctd\u003e250\u003c\/td\u003e\n        \u003ctd\u003e4-Stroke\u003c\/td\u003e\n        \u003ctd\u003e2012–2018\u003c\/td\u003e\n        \u003ctd\u003e6P2-45300-43-8D\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha\u003c\/td\u003e\n        \u003ctd\u003eF250XCA\u003c\/td\u003e\n        \u003ctd\u003e250\u003c\/td\u003e\n        \u003ctd\u003e4-Stroke\u003c\/td\u003e\n        \u003ctd\u003e2017\u003c\/td\u003e\n        \u003ctd\u003e6P2-45300-43-8D\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha\u003c\/td\u003e\n        \u003ctd\u003eF250TXR\u003c\/td\u003e\n        \u003ctd\u003e250\u003c\/td\u003e\n        \u003ctd\u003e4-Stroke\u003c\/td\u003e\n        \u003ctd\u003e2005–2011\u003c\/td\u003e\n        \u003ctd\u003e6P2-45300-41-8D, 6P2-45300-42-8D\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha\u003c\/td\u003e\n        \u003ctd\u003eF250BTXR\u003c\/td\u003e\n        \u003ctd\u003e250\u003c\/td\u003e\n        \u003ctd\u003e4-Stroke\u003c\/td\u003e\n        \u003ctd\u003e2008–2009\u003c\/td\u003e\n        \u003ctd\u003e6P2-45300-41-8D, 6P2-45300-42-8D\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha\u003c\/td\u003e\n        \u003ctd\u003eF250TXRD\u003c\/td\u003e\n        \u003ctd\u003e250\u003c\/td\u003e\n        \u003ctd\u003e4-Stroke\u003c\/td\u003e\n        \u003ctd\u003e2005\u003c\/td\u003e\n        \u003ctd\u003e6P2-45300-41-8D\u003c\/td\u003e\n        \u003ctd\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha\u003c\/td\u003e\n        \u003ctd\u003eF225TXR\u003c\/td\u003e\n        \u003ctd\u003e225\u003c\/td\u003e\n        \u003ctd\u003e4-Stroke\u003c\/td\u003e\n        \u003ctd\u003e2002–2011\u003c\/td\u003e\n        \u003ctd\u003e6P2-45300-41-8D, 6P2-45300-42-8D\u003c\/td\u003e\n        \u003ctd\u003eAlso fits 225 HP 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\u003eProduct Type\u003c\/dt\u003e\n\u003cdd\u003eComplete Lower Unit (Gearcase)\u003c\/dd\u003e\n  \u003cdt\u003eInstallation\u003c\/dt\u003e\n\u003cdd\u003eDirect bolt-on replacement\u003c\/dd\u003e\n  \u003cdt\u003eFuel Type\u003c\/dt\u003e\n\u003cdd\u003eGasoline\u003c\/dd\u003e\n  \u003cdt\u003eConnection\u003c\/dt\u003e\n\u003cdd\u003eDirect driveshaft spline connection\u003c\/dd\u003e\n  \u003cdt\u003eHousing Material\u003c\/dt\u003e\n\u003cdd\u003eMarine-grade aluminum\u003c\/dd\u003e\n  \u003cdt\u003eHousing Color\u003c\/dt\u003e\n\u003cdd\u003eBlack (requires painting to match engine)\u003c\/dd\u003e\n  \u003cdt\u003eDimensions (H x W x L)\u003c\/dt\u003e\n\u003cdd\u003e130.0 x 22.5 x 77.0 cm\u003c\/dd\u003e\n  \u003cdt\u003eFitting Type\u003c\/dt\u003e\n\u003cdd\u003eStandard rotation (right-hand)\u003c\/dd\u003e\n  \u003cdt\u003eWater Pump\u003c\/dt\u003e\n\u003cdd\u003eIncluded, pre-installed\u003c\/dd\u003e\n  \u003cdt\u003eGear Ratio\u003c\/dt\u003e\n\u003cdd\u003e2:1\u003c\/dd\u003e\n  \u003cdt\u003eShaft Length\u003c\/dt\u003e\n\u003cdd\u003e25\" (635 mm)\u003c\/dd\u003e\n  \u003cdt\u003eWater Pickup\u003c\/dt\u003e\n\u003cdd\u003eDual water pickup\u003c\/dd\u003e\n  \u003cdt\u003eWarranty\u003c\/dt\u003e\n\u003cdd\u003e3-Year No-Fault Warranty\u003c\/dd\u003e\n  \u003cdt\u003eOther Technical Attributes\u003c\/dt\u003e\n\u003cdd\u003eWater-cooled bearing carrier\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 Complete Lower Unit Assembly (90-422-B25F) with \u003cspan style=\"color:#d0021b;\"\u003epre-installed water pump\u003c\/span\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eInstallation Notes\u003c\/h2\u003e\n\u003col\u003e\n  \u003cli\u003eDisconnect the battery and secure the shift linkage.\u003c\/li\u003e\n  \u003cli\u003ePosition a suitable container and drain the old gearcase oil completely.\u003c\/li\u003e\n  \u003cli\u003eRemove the mounting bolts securing the lower unit to the engine's midsection.\u003c\/li\u003e\n  \u003cli\u003eCarefully lower the old unit away from the engine, ensuring the driveshaft disengages without binding.\u003c\/li\u003e\n  \u003cli\u003eThoroughly clean the mating surfaces on the engine.\u003c\/li\u003e\n  \u003cli\u003eApply a light coat of marine-grade grease to the new unit's driveshaft and shift shaft splines.\u003c\/li\u003e\n  \u003cli\u003eCarefully raise the new lower unit, aligning the driveshaft, water tube, and shift shaft.\u003c\/li\u003e\n  \u003cli\u003eInstall the mounting bolts and torque them to the manufacturer's specified values in the correct sequence.\u003c\/li\u003e\n  \u003cli\u003eReconnect the shift linkage and confirm smooth engagement of forward, neutral, and reverse gears.\u003c\/li\u003e\n  \u003cli\u003eFill the new gearcase with the correct type and amount of marine gear lubricant.\u003c\/li\u003e\n  \u003cli\u003eReconnect the battery. Before open water use, test the engine's operation, cooling, and shifting in a safe, controlled environment.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch2\u003eTroubleshooting \u0026amp; FAQ\u003c\/h2\u003e\n\u003cdetails\u003e\u003csummary\u003eHow do I confirm this lower unit fits my Yamaha outboard?\u003c\/summary\u003e\u003cp\u003eCheck your engine's model number and year against the compatibility chart. This unit fits specific F250 and F225 models with a 25\" shaft and 2:1 gear ratio. Also, verify your OEM part number matches the replacements listed.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eDo I need to paint this gearcase?\u003c\/summary\u003e\u003cp\u003eYes. The housing is supplied in a base black color and requires painting with a marine-grade paint to color-match your specific Yamaha outboard and provide an additional layer of corrosion protection.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eWhat are the signs my old lower unit is failing?\u003c\/summary\u003e\u003cp\u003eCommon signs include metal shavings in the gear oil, a grinding or clunking noise when shifting or running, water in the oil (milky appearance), or a bent\/damaged propshaft.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eDoes this unit include the water pump and other hardware?\u003c\/summary\u003e\u003cp\u003eYes, a complete new water pump assembly is pre-installed for your convenience. However, mounting hardware (bolts, nuts, washers) is not typically included and you should plan to reuse your existing hardware if it is in good condition.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eWhat gear oil should I use?\u003c\/summary\u003e\u003cp\u003eUse a high-quality marine gear lubricant that meets API GL-5 specifications, as recommended by your engine's manufacturer service manual.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eIs this a standard or counter-rotation model?\u003c\/summary\u003e\u003cp\u003eThis is a standard, right-hand rotation lower unit.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eOEM vs. Aftermarket?\u003c\/summary\u003e\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\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eShipping speed \u0026amp; cost\u003c\/summary\u003e\u003cp\u003eWe ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.\u003c\/p\u003e\u003c\/details\u003e\n\u003cdetails\u003e\u003csummary\u003eWarranty \u0026amp; returns\u003c\/summary\u003e\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\u003c\/details\u003e\n\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\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 QC.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/section\u003e","brand":"SeaSierra","offers":[{"title":"Default Title","offer_id":50623297356091,"sku":"422-B25F","price":1395.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0826\/8673\/8747\/files\/422-B25F_18cc62ea-282a-4c0c-84f7-27f5dc226b65.jpg?v=1759630691","url":"https:\/\/seasierra.com\/products\/sei-yamaha-lower-unit-90-422-b25f-fits-yamaha-f250-outboards-with-25-driveshaft-replaces-6p2-45300-41-8d-43-8d","provider":"SeaSierra","version":"1.0","type":"link"}