{"title":"Mercury 40 HP 4-Stroke Outboard Engine Parts","description":"\u003csection id=\"hero\" style=\"padding:16px; border:1px solid #e5e7eb; border-radius:8px; max-width:1000px;\"\u003e\n  \u003cp\u003e\n    This page is dedicated to Mercury 4‑Stroke 40 HP outboard engines and helps you quickly find compatible parts and service information. Below you’ll find maintenance tips, common replacement parts, and troubleshooting guidance. You can also browse our main Mercury collection anytime. Scroll to the bottom of this page to start browsing parts for this engine, and remember that on the collection page you can use the Filter \u0026amp; Sort controls to narrow results by horsepower, year range, and part category.\n  \u003c\/p\u003e\n  \u003ca href=\"https:\/\/seasierra.com\/collections\/mercury-outboard-parts\" style=\"display:inline-block; padding:10px 16px; background:#0ea5e9; color:#fff; text-decoration:none; border-radius:6px;\"\u003eBrowse All Mercury Parts\u003c\/a\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"identify-model\" style=\"max-width:1000px; padding:16px;\"\u003e\n  \u003ch2\u003eHow to Identify Your 40 HP Model\u003c\/h2\u003e\n  \u003cul\u003e\n    \u003cli\u003eLocate the serial\/nameplate on the transom bracket or swivel bracket. Record the complete serial number to confirm parts.\u003c\/li\u003e\n    \u003cli\u003eRead the cowl decals and model code: “FourStroke” and “EFI” indicate a 4‑stroke fuel‑injected model. Suffixes may denote shaft length (L\/XL) and control type (tiller\/remote).\u003c\/li\u003e\n    \u003cli\u003eGearcase variant: Standard vs Command Thrust\/BigFoot (larger gearcase and prop). Many service parts are shared, but gearcase parts and propellers can differ.\u003c\/li\u003e\n    \u003cli\u003e4‑Stroke cues: engine oil fill\/cap and oil filter under the cowl; no 2‑stroke oil tank on the transom.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"engine-overview\" style=\"max-width:1000px; padding:16px;\"\u003e\n  \u003ch2\u003eEngine Platform Overview\u003c\/h2\u003e\n  \u003ch3\u003eMercury 40 HP FourStroke EFI (Inline‑4 Platform)\u003c\/h3\u003e\n  \u003ctable style=\"width:100%; border-collapse:collapse;\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:8px;\"\u003eFeature\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:8px;\"\u003eDescription\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eConfiguration\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eInline‑4 EFI 4‑Stroke platform used on many 40\/50\/60 HP FourStroke models.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eCommon Models\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003e40 EFI FourStroke (standard gearcase), 40 Command Thrust\/BigFoot (larger gearcase), L\/XL shaft, tiller or remote control variants.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eAdvantages\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eGood fuel economy and low noise; broad parts availability; many routine service items shared across the 40\/50\/60 HP family.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eNotes\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eVerify Standard vs Command Thrust before ordering propellers and gearcase parts. Certain service items may change with serial number breaks; confirm with your serial plate.\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"service-kits\" style=\"max-width:1000px; padding:16px;\"\u003e\n  \u003ch2\u003eRoutine Maintenance \u0026amp; Service Parts\u003c\/h2\u003e\n  \u003cp\u003eIntervals below are general guidelines for many Mercury FourStroke 40 HP models. Always follow your official service manual and your specific serial number’s recommendations.\u003c\/p\u003e\n  \u003ctable style=\"width:100%; border-collapse:collapse;\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:8px;\"\u003eItem\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:8px;\"\u003eInterval*\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:8px;\"\u003eRemarks\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:8px;\"\u003eParts Link\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eEngine oil + filter\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eEvery 100 hours or annually\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eWarm engine before draining; replace crush washer if applicable.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/service-maintenance-kits\"\u003eService \u0026amp; Maintenance Kits\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eGear oil (lower unit)\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eEvery 100 hours or annually; before winter storage\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eInspect for water intrusion (milky oil) and metal shavings; replace drain gaskets.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/mercury-outboard-parts\"\u003eMercury Outboard Parts\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eSpark plugs\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eInspect every 100 hours; replace ~300 hours or as needed\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eCheck gap and replace any fouled or worn plugs.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/spark-plug\"\u003eSpark Plugs\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eFuel filter \/ inline filter\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eEvery 100 hours or annually\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eReplace more often with ethanol fuel or contaminated fuel systems.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/fuel-filters-1\"\u003eFuel Filters\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eWater pump impeller \/ kit\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eEvery 2 seasons or 200–300 hours (sooner for sandy\/silty water)\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eCritical for cooling; inspect housing and key, not just the impeller.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/mercury-water-pump-repair-kits\"\u003eMercury Water Pump Repair Kits\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eAnodes (corrosion protection)\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eInspect every 50 hours; replace when ~50% depleted\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eMatch anode material to your water (fresh, brackish, salt). Keep paint off anodes.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/anodes\"\u003eAnodes\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n  \u003cp style=\"font-size:12px; color:#6b7280; margin-top:8px;\"\u003e*Follow your service manual for exact intervals and procedures based on serial number.\u003c\/p\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"common-parts\" style=\"max-width:1000px; padding:16px;\"\u003e\n  \u003ch2\u003eFrequently Used Parts Categories\u003c\/h2\u003e\n  \u003cul\u003e\n    \u003cli\u003eRoutine Service: \u003ca href=\"https:\/\/seasierra.com\/collections\/service-maintenance-kits\"\u003eService \u0026amp; Maintenance Kits\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eCooling System: \u003ca href=\"https:\/\/seasierra.com\/collections\/mercury-water-pump-repair-kits\"\u003eMercury Water Pump Repair Kits\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eFuel System: \u003ca href=\"https:\/\/seasierra.com\/collections\/fuel-filters-1\"\u003eFuel Filters\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eIgnition \/ Electrical: \u003ca href=\"https:\/\/seasierra.com\/collections\/electrical-items\"\u003eElectrical Items\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eCorrosion Protection: \u003ca href=\"https:\/\/seasierra.com\/collections\/anodes\"\u003eAnodes\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eGearcase Seals: \u003ca href=\"https:\/\/seasierra.com\/collections\/mercury-lower-unit-seal-kits\"\u003eMercury Lower Unit Seal Kits\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003ePropellers: \u003ca href=\"https:\/\/seasierra.com\/collections\/propellers\"\u003ePropellers\u003c\/a\u003e\n\u003c\/li\u003e\n  \u003c\/ul\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"troubleshooting\" style=\"max-width:1000px; padding:16px;\"\u003e\n  \u003ch2\u003eCommon Symptoms \u0026amp; Quick Checks\u003c\/h2\u003e\n  \u003ctable style=\"width:100%; border-collapse:collapse;\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:8px;\"\u003eSymptom\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:8px;\"\u003eCheck First\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:8px;\"\u003eRelated Parts\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eWeak telltale stream or overheat alarm\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eDebris in intake screens, clogged telltale, worn impeller, thermostat stuck\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eWater pump kit, thermostat, intake screen, gaskets\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eHard starting or rough idle\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eStale fuel, weak battery, restricted fuel filter, fouled plugs, air leaks at primer bulb\/lines\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eFuel filter, spark plugs, injectors, fuel lines\/primer bulb\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003ePoor acceleration or power loss\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eDamaged or wrong‑pitch prop, clogged filter, low compression, sensor faults\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003ePropeller, fuel filter, spark plugs, sensors\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px;\"\u003eGearcase noise or metal in gear oil\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eLow\/contaminated gear oil, leaking seals, fishing line on prop shaft, worn bearings\u003c\/td\u003e\n        \u003ctd style=\"padding:8px;\"\u003eLower unit seal kit, bearings, drain\/fill gaskets, gear lube\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"faq\" style=\"max-width:1000px; padding:16px;\"\u003e\n  \u003ch2\u003eFAQs\u003c\/h2\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eAre parts interchangeable across different years or the 40\/50\/60 FourStroke family?\u003c\/summary\u003e\n    \u003cp\u003eMany routine service items (filters, anodes, some ignition and cooling parts) are shared within the 40\/50\/60 FourStroke family, but changes occur with serial number breaks and gearcase type (Standard vs Command Thrust). Always confirm by serial number.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhen should I replace the water pump impeller?\u003c\/summary\u003e\n    \u003cp\u003eTypically every two seasons or 200–300 hours, and immediately if you notice weak telltale flow or an overheat alarm. Shorten the interval if operating in sandy or silty water.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow often should I change the lower unit gear oil?\u003c\/summary\u003e\n    \u003cp\u003eEvery 100 hours or annually, and before off‑season storage. Inspect for milky oil (water intrusion) or metal particles which indicate seal or gear wear.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhat information do you need to confirm part compatibility?\u003c\/summary\u003e\n    \u003cp\u003ePlease provide the engine serial number, model description (e.g., 40 EFI FourStroke), shaft length (L\/XL), gearcase type (Standard or Command Thrust\/BigFoot), and control type (tiller\/remote). Photos of the nameplate and the part area help as well.\u003c\/p\u003e\n  \u003c\/details\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"cta\" style=\"padding:16px; border-top:1px solid #e5e7eb; max-width:1000px;\"\u003e\n  \u003cp\u003eReady to find the right parts? Browse the main Mercury collection to filter by horsepower, year, and model.\u003c\/p\u003e\n  \u003ca href=\"https:\/\/seasierra.com\/collections\/mercury-outboard-parts\" style=\"display:inline-block; padding:10px 16px; background:#0ea5e9; color:#fff; text-decoration:none; border-radius:6px;\"\u003eShop Mercury Outboard Parts\u003c\/a\u003e\n  \u003cp style=\"margin-top:8px; font-size:12px; color:#6b7280;\"\u003eIf you’re unsure about your model, send us a photo of the nameplate and the part you need and we’ll help verify compatibility.\u003c\/p\u003e\n\u003c\/section\u003e","products":[],"url":"https:\/\/seasierra.com\/collections\/mercury-40-hp-4-stroke-outboard-engine-parts.oembed","provider":"SeaSierra","version":"1.0","type":"link"}