{"product_id":"878408a1-power-trim-tilt-o-ring-repair-kit-for-mercury-v6-135-300hp-jlm-marine","title":"878408A1 Power Trim \u0026 Tilt O-Ring Repair Kit for Mercury V6 135-300HP | JLM Marine","description":"\n\u003ch2\u003ePower Trim \u0026amp; Tilt O-Ring Repair Kit for Mercury V6 135-300HP\u003c\/h2\u003e\n\u003cp\u003eThis premium Power Trim \u0026amp; Tilt O-Ring Repair Kit is engineered for Mercury and Mariner V6 outboard motors ranging from 135HP to 300HP (1998 and newer). It ensures reliable hydraulic sealing and prevents fluid leaks in your power trim cylinder, restoring smooth tilt and trim operation.\u003c\/p\u003e\n\u003cp\u003eThis kit directly replaces OEM part numbers \u003cstrong\u003e878408A1\u003c\/strong\u003e, \u003cstrong\u003e878408A 1\u003c\/strong\u003e, \u003cstrong\u003e25-878408A1\u003c\/strong\u003e, and \u003cstrong\u003e8M0142341\u003c\/strong\u003e. Upgraded with high-grade Viton and Urethane seals, it provides a superior, long-lasting solution compared to standard factory seals that often degrade over time.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eComprehensive O-Ring kit for power trim and tilt cylinder rebuilds\u003c\/li\u003e\n\u003cli\u003eFits Mercury V6 135-300HP, Verado 4-Cyl, and Gen 3 engines (1998 \u0026amp; UP)\u003c\/li\u003e\n\u003cli\u003eManufactured with premium Viton and High-Grade Urethane for maximum durability\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003ePart Number Cross-Reference\u003c\/h2\u003e\n\u003cp\u003eUse this table to confirm equivalent part numbers across OEM and aftermarket sources.\u003c\/p\u003e\n\u003cdiv style=\"overflow-x:auto;\"\u003e\n\u003ctable border=\"1\" cellpadding=\"8\" cellspacing=\"0\" style=\"border-collapse:collapse; width:100%;\"\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 OEM\u003c\/td\u003e\n\u003ctd\u003e878408A1, 878408A 1, 878408A01, 25-878408A1\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercury (Superseded)\u003c\/td\u003e\n\u003ctd\u003e855998A10, 855998A11, 8M0142341\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSierra Marine\u003c\/td\u003e\n\u003ctd\u003e18-2682 (Reference)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAftermarket\u003c\/td\u003e\n\u003ctd\u003eFSM030, FSM010, 811612A, 335-250, REC878408A1\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eCompatible Engine Models\u003c\/h2\u003e\n\u003cp\u003eConfirm your engine model\/year in the table below. For Mercury owners, here's a guide to help you identify your engine's serial\/model: \u003ca href=\"https:\/\/jlmmarine.com\/blogs\/serial-number-guide\/mercury-outboard-serial-number-guide\" rel=\"nofollow noopener\" target=\"_blank\"\u003eMercury Serial Number Guide\u003c\/a\u003e. You can also review exploded diagrams to verify part numbers: \u003ca href=\"https:\/\/jlmmarine.com\/blogs\/diagrams\/mercury-parts-catalog\" rel=\"nofollow noopener\" target=\"_blank\"\u003eMercury Parts Diagrams \u0026amp; Catalog\u003c\/a\u003e.\u003c\/p\u003e\n\u003cdiv style=\"overflow-x:auto;\"\u003e\n\u003ctable border=\"1\" cellpadding=\"8\" cellspacing=\"0\" style=\"border-collapse:collapse; width:100%;\"\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eBrand\u003c\/th\u003e\n\u003cth\u003eModel \/ Series\u003c\/th\u003e\n\u003cth\u003eRated HP\u003c\/th\u003e\n\u003cth\u003eEngine Type\u003c\/th\u003e\n\u003cth\u003eYear Range\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercury \/ Mariner\u003c\/td\u003e\n\u003ctd\u003eV6 Outboards\u003c\/td\u003e\n\u003ctd\u003e135 - 250 HP\u003c\/td\u003e\n\u003ctd\u003eV6 2-Stroke \/ EFI\u003c\/td\u003e\n\u003ctd\u003e1998 and UP\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercury\u003c\/td\u003e\n\u003ctd\u003eGen 3 Outboards\u003c\/td\u003e\n\u003ctd\u003e135 - 250 HP\u003c\/td\u003e\n\u003ctd\u003eV6\u003c\/td\u003e\n\u003ctd\u003e2001 and UP\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercury\u003c\/td\u003e\n\u003ctd\u003eDFI \/ Optimax \/ Pro XS\u003c\/td\u003e\n\u003ctd\u003e135 - 300 HP\u003c\/td\u003e\n\u003ctd\u003e2.5L \u0026amp; 3.0L V6\u003c\/td\u003e\n\u003ctd\u003e2000 - 2018\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercury\u003c\/td\u003e\n\u003ctd\u003eVerado\u003c\/td\u003e\n\u003ctd\u003e135 - 200 HP\u003c\/td\u003e\n\u003ctd\u003e4-Cylinder 4-Stroke\u003c\/td\u003e\n\u003ctd\u003e2006 - 2014\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMercury\u003c\/td\u003e\n\u003ctd\u003eJet Drive\u003c\/td\u003e\n\u003ctd\u003e110 HP\u003c\/td\u003e\n\u003ctd\u003e6-Cylinder\u003c\/td\u003e\n\u003ctd\u003e2000 - 2005\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003eTechnical Specifications\u003c\/h2\u003e\n\u003cdiv style=\"overflow-x:auto;\"\u003e\n\u003ctable border=\"1\" cellpadding=\"8\" cellspacing=\"0\" style=\"border-collapse:collapse; width:100%;\"\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eSpecification\u003c\/th\u003e\n\u003cth\u003eValue\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eOEM Number\u003c\/td\u003e\n\u003ctd\u003e878408A1\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eReplaces\u003c\/td\u003e\n\u003ctd\u003e878408A1, 25-878408A1, 855998A11, 8M0142341\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eApplication\u003c\/td\u003e\n\u003ctd\u003ePower Trim \u0026amp; Tilt Cylinder Seal Repair\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMaterial\u003c\/td\u003e\n\u003ctd\u003eViton \u0026amp; High-Grade Urethane\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eEngine Configuration\u003c\/td\u003e\n\u003ctd\u003eV6 \/ 4-Cyl Verado\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/div\u003e\n\n\u003ch2\u003ePackage Contents\u003c\/h2\u003e\n\u003cp\u003eThis repair kit includes all necessary O-rings and seals to rebuild your power trim cylinder (Note: Contains seals for the cylinders only, not the entire assembly):\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\u003cspan style=\"color:red;\"\u003e26x Various O-Rings (Viton \/ Urethane)\u003c\/span\u003e\u003c\/li\u003e\n\u003cli\u003e\u003cspan style=\"color:red;\"\u003e1x Trilobe Pin (OEM 821539)\u003c\/span\u003e\u003c\/li\u003e\n\u003cli\u003e\u003cspan style=\"color:red;\"\u003e2x Poppet Assembly\u003c\/span\u003e\u003c\/li\u003e\n\u003cli\u003e\u003cspan style=\"color:red;\"\u003e1x Valve Assembly\u003c\/span\u003e\u003c\/li\u003e\n\u003cli\u003e\u003cspan style=\"color:red;\"\u003e1x Tilt Wiper Seal \u0026amp; 2x Wiper Seals\u003c\/span\u003e\u003c\/li\u003e\n\u003cli\u003e\u003cspan style=\"color:red;\"\u003eManifold Screws \u0026amp; Filter Caps\u003c\/span\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eInstallation Guide\u003c\/h2\u003e\n\u003col\u003e\n\u003cli\u003eEnsure the outboard motor is securely supported and the trim system is depressurized before beginning work.\u003c\/li\u003e\n\u003cli\u003eRemove the power trim and tilt assembly from the engine bracket following your Mercury service manual.\u003c\/li\u003e\n\u003cli\u003eCarefully disassemble the trim cylinders. Take note of the orientation of all internal components.\u003c\/li\u003e\n\u003cli\u003eRemove old seals, O-rings, and wipers. Clean all cylinder walls and grooves thoroughly with a lint-free cloth and appropriate solvent.\u003c\/li\u003e\n\u003cli\u003eInspect the cylinder walls and rods for scoring, pitting, or corrosion. Replace hard parts if necessary.\u003c\/li\u003e\n\u003cli\u003eInstall the new Viton and Urethane seals from the kit. Lightly lubricate all new O-rings with premium power trim fluid before installation to prevent tearing.\u003c\/li\u003e\n\u003cli\u003eReassemble the cylinders and reinstall the trim unit onto the outboard.\u003c\/li\u003e\n\u003cli\u003eFill the reservoir with the recommended Mercury Power Trim fluid, bleed the system of air by cycling it up and down several times, and check for leaks.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch2\u003eTroubleshooting \u0026amp; FAQ\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eQ: How do I confirm this kit fits my Mercury engine?\u003c\/strong\u003e\u003cbr\u003e\nA: Verify your engine is a V6 (135-250HP) from 1998 or newer, a 2.5L\/3.0L DFI\/Optimax, or a 4-Cylinder Verado (135-200HP). You can also cross-reference OEM part numbers 878408A1 or 25-878408A1.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: Why are my original trim seals leaking?\u003c\/strong\u003e\u003cbr\u003e\nA: Factory OEM seals from certain eras are known to soften and degrade over 5-10 years of use in harsh marine environments. This kit uses upgraded Viton and Urethane materials designed to resist degradation and outlast the originals.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: Does this kit rebuild the entire trim and tilt unit?\u003c\/strong\u003e\u003cbr\u003e\nA: No, this specific kit (878408A1) contains the O-rings and seals for the cylinders only. It does not contain all the O-rings for the entire valve body\/manifold assembly.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: Is this an OEM or aftermarket part?\u003c\/strong\u003e\u003cbr\u003e\nA: This listing is a premium aftermarket replacement part. We build to exceed OEM specifications using superior-grade Viton and Urethane materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: How fast do you ship and how much does it cost?\u003c\/strong\u003e\u003cbr\u003e\nA: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eQ: What is your warranty and return policy?\u003c\/strong\u003e\u003cbr\u003e\nA: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused \u0026amp; in original condition); please see our policy page or reach out for instructions.\u003c\/p\u003e\n\n\u003ch2\u003eImportant Notes\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eVerify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.\u003c\/li\u003e\n\u003cli\u003eThis product is an aftermarket replacement part and is not an OEM component.\u003c\/li\u003e\n\u003cli\u003eProfessional installation is recommended to ensure safety and optimal performance.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhy Choose JLM MARINE?\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eQuality Assured:\u003c\/strong\u003e As a trusted manufacturer for over 20 years, we supply top marine brands globally.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFast Global Shipping:\u003c\/strong\u003e Free delivery worldwide in 5–15 days.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDirect from Manufacturer:\u003c\/strong\u003e Competitive pricing without compromising quality.\u003c\/li\u003e\n\u003c\/ul\u003e\n","brand":"JLM Marine","offers":[{"title":"Default Title","offer_id":53302458057017,"sku":"25SK467","price":47.77,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0885\/0433\/6697\/files\/878408A1.jpg?v=1779068250","url":"https:\/\/jlmmarine.com\/products\/878408a1-power-trim-tilt-o-ring-repair-kit-for-mercury-v6-135-300hp-jlm-marine","provider":"JLM Marine Boat Parts Limited","version":"1.0","type":"link"}