{"product_id":"lower-unit-gearcase-fits-yamaha-v4-115hp-130hp-2-stroke-outboards-replaces-602-90-405-a20","title":"Lower Unit Gearcase – Fits Yamaha V4 115HP \u0026 130HP 2-Stroke Outboards (Replaces 602-90-405-A20)","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 \u003cstrong\u003eLower Unit Gearcase – Fits Yamaha V4 115HP \u0026amp; 130HP 2-Stroke Outboards\u003c\/strong\u003e is an aftermarket solution designed for Yamaha V4 115HP and 130HP 2-stroke engines requiring a 20\" shaft, standard right-hand rotation, and a 2:1 gear ratio. It offers a reliable, direct-fit replacement to get your outboard back in service.\u003c\/p\u003e\n\u003cp\u003eIt directly cross-references with SEI part number 602-90-405-A20.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003eEngineered for direct bolt-on installation.\u003c\/li\u003e\n  \u003cli\u003eFinished in durable black paint.\u003c\/li\u003e\n  \u003cli\u003eExclusively compatible with 2-Stroke engine applications.\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\u003c\/td\u003e\n        \u003ctd\u003e602-90-405-A20\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\u003eModel\u003c\/th\u003e\n        \u003cth\u003eRated HP\u003c\/th\u003e\n        \u003cth\u003eStroke\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\u003eV4\u003c\/td\u003e\n        \u003ctd\u003e115\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003eStandard rotation only\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd\u003eYamaha\u003c\/td\u003e\n        \u003ctd\u003eV4\u003c\/td\u003e\n        \u003ctd\u003e130\u003c\/td\u003e\n        \u003ctd\u003e2-Stroke\u003c\/td\u003e\n        \u003ctd\u003eStandard rotation only\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\u003eReplacement Lower Unit Gearcase\u003c\/dd\u003e\n  \u003cdt\u003eInstallation\u003c\/dt\u003e\n\u003cdd\u003eDirect bolt-on replacement\u003c\/dd\u003e\n  \u003cdt\u003eGear Ratio\u003c\/dt\u003e\n\u003cdd\u003e2:1\u003c\/dd\u003e\n  \u003cdt\u003eRotation\u003c\/dt\u003e\n\u003cdd\u003eStandard (Right-Hand)\u003c\/dd\u003e\n  \u003cdt\u003eShaft Length\u003c\/dt\u003e\n\u003cdd\u003e20\" (508 mm)\u003c\/dd\u003e\n  \u003cdt\u003eHousing Color\u003c\/dt\u003e\n\u003cdd\u003eBlack\u003c\/dd\u003e\n  \u003cdt\u003eApplication\u003c\/dt\u003e\n\u003cdd\u003e2-Stroke engines only\u003c\/dd\u003e\n  \u003cdt\u003eOther Technical Attributes\u003c\/dt\u003e\n\u003cdd\u003eWill not work on 4-Stroke Engine applications\u003c\/dd\u003e\n  \u003cdt\u003eProduct Dimensions\u003c\/dt\u003e\n\u003cdd\u003e114.0 x 22.0 x 70.5 cm\u003c\/dd\u003e\n\u003c\/dl\u003e\n\n\u003ch2\u003eWhat’s in the Box\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cspan style=\"color:#d0021b;\"\u003e1 x\u003c\/span\u003e Complete Lower Unit Gearcase Assembly (602-90-405-A20)\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eInstallation Notes\u003c\/h2\u003e\n\u003col\u003e\n  \u003cli\u003eDisconnect the battery and spark plug wires for safety.\u003c\/li\u003e\n  \u003cli\u003ePlace a drain pan under the lower unit and remove the gear oil drain and vent screws to empty the oil.\u003c\/li\u003e\n  \u003cli\u003eRemove the bolts securing the lower unit to the outboard's midsection.\u003c\/li\u003e\n  \u003cli\u003eCarefully lower the old gearcase, ensuring the shift shaft linkage is disconnected.\u003c\/li\u003e\n  \u003cli\u003eClean the mating surfaces on the engine leg and install a new water pump housing base gasket.\u003c\/li\u003e\n  \u003cli\u003eAlign the driveshaft, water tube, and shift shaft, then raise the new gearcase into position.\u003c\/li\u003e\n  \u003cli\u003eInstall and tighten the mounting bolts to the manufacturer's recommended torque specifications.\u003c\/li\u003e\n  \u003cli\u003eReconnect the shift shaft linkage and confirm proper gear engagement (Forward-Neutral-Reverse).\u003c\/li\u003e\n  \u003cli\u003eRefill the gearcase with fresh, high-quality marine gear lubricant according to the manufacturer's procedure. Install new drain screw gaskets and tighten screws securely.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch2\u003eTroubleshooting \u0026amp; FAQ\u003c\/h2\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eHow do I confirm this fits my specific engine model and year?\u003c\/summary\u003e\n  \u003cp\u003eThis lower unit is designed for Yamaha V4 115HP \u0026amp; 130HP 2-Stroke outboards with a 20\" shaft. The most reliable method is to compare the specifications (gear ratio, shaft length, rotation) and visual details in the product photos with your existing lower unit. If any specification differs, do not purchase.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWill this work on my 4-Stroke Yamaha engine?\u003c\/summary\u003e\n  \u003cp\u003eNo. This lower unit is explicitly designed for 2-Stroke engine applications only and is not compatible with any 4-Stroke models.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWhat are the signs that my current lower unit is failing?\u003c\/summary\u003e\n  \u003cp\u003eCommon symptoms include metallic grinding or clunking noises, difficulty shifting gears, visible metal shavings in the gear oil (a \"milky\" appearance also indicates water intrusion), or vibrations felt through the hull during operation. If you notice any of these signs, inspection is recommended.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWhat maintenance is required for this lower unit?\u003c\/summary\u003e\n  \u003cp\u003eRegularly inspect and change the gear oil at least once per season or every 100 hours of use, whichever comes first. Use a high-quality marine gear lubricant specified for your outboard. Always check for water intrusion (milky oil), which indicates a seal failure that must be addressed immediately.\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 9001 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\/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":50623297618235,"sku":"405-A20","price":1195.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0826\/8673\/8747\/files\/405-A20_9424f72d-363c-42df-893d-13330e82be48.jpg?v=1759630701","url":"https:\/\/seasierra.com\/products\/lower-unit-gearcase-fits-yamaha-v4-115hp-130hp-2-stroke-outboards-replaces-602-90-405-a20","provider":"SeaSierra","version":"1.0","type":"link"}