{"title":"GM 4-Stroke 125HP Marine Engine Parts","description":"\u003csection id=\"hero\" style=\"padding:16px; border:1px solid #e5e7eb; border-radius:8px;\"\u003e\n  \u003cp\u003eThis page is for GM 4-Stroke 125HP outboard engines. It helps you find compatible parts and service information, including maintenance tips, common replacement parts, and troubleshooting guidance. You can also browse the main MerCruiser collection for GM-based marine engines. Scroll to the bottom of this page to start browsing parts for this engine, and on the collection page use the “Filter \u0026amp; Sort” controls to narrow results by horsepower, year range, and part category.\u003c\/p\u003e\n  \u003cp\u003e\n    \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser\" style=\"display:inline-block; padding:10px 16px; background:#0ea5e9; color:#fff; text-decoration:none; border-radius:6px;\"\u003eBrowse All MerCruiser Parts\u003c\/a\u003e\n  \u003c\/p\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"identify-model\"\u003e\n  \u003ch2\u003eHow to Identify Your 125HP Model\u003c\/h2\u003e\n  \u003cul\u003e\n    \u003cli\u003eFind the nameplate\/serial sticker on the transom bracket or swivel bracket; some models also have an ID decal on the engine cover.\u003c\/li\u003e\n    \u003cli\u003eModel codes often include horsepower and suffixes for shaft length (S\/L\/XL), control\/starting type (R = remote, E = electric start), and sometimes a year or revision letter.\u003c\/li\u003e\n    \u003cli\u003eFor 4-stroke versions, check for EFI labels and an oxygen sensor on the exhaust—these indicate an EFI platform versus older carbureted setups.\u003c\/li\u003e\n    \u003cli\u003eRecord the full model\/serial data before ordering; small differences (gear ratio, charging system, shaft length) can change parts compatibility.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"engine-overview\"\u003e\n  \u003ch2\u003ePlatform Overview\u003c\/h2\u003e\n  \u003ch3\u003eInline-4 EFI 4‑Stroke (125 HP Class)\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 outboard platform; electronic fuel injection for reliable starts and fuel economy.\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;\"\u003e125 HP 4‑stroke models with remote controls and long\/extra‑long shafts; variants may include saltwater corrosion‑resistant packages.\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 efficiency, smooth idle, strong mid‑range torque, and lower emissions compared with 2‑stroke platforms.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eNotes\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eMatch parts by serial\/model ID. Cooling, fuel, and ignition components can vary by year, shaft length, and charging system output.\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\n  \u003ch3\u003eInline-4 Carbureted 4‑Stroke (Earlier\/Alt. Variants)\u003c\/h3\u003e\n  \u003ctable style=\"width:100%; border-collapse:collapse; margin-top:12px;\"\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 4‑stroke with carburetors; simpler fuel system but requires periodic synchronization and cleaning.\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;\"\u003e115–130 HP class 4‑stroke models using carbureted induction; some share ignition and cooling parts with EFI 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;\"\u003eStraightforward service, good parts availability, and robust mid‑range performance.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eNotes\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eFloat settings, jetting, and link‑and‑sync procedures are model‑specific—verify against the model\/serial number.\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\"\u003e\n  \u003ch2\u003eRoutine Maintenance \u0026amp; Service Parts\u003c\/h2\u003e\n  \u003cp\u003eIntervals are general guidelines for 4‑stroke outboards. Always confirm procedures and timing with your official service manual and follow local operating conditions.\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;\"\u003e100 hours or annually\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eWarm engine before draining; replace crush washer; verify level after run‑up.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-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;\"\u003e100 hours or annually\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eInspect for metal or milky oil (water intrusion). Replace seals if contamination is found.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/lower-unit-seal-kits\"\u003eLower Unit Seal Kits\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 100 hours; replace 300 hours\/3 years\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eCheck gap and color; replace if fouled or worn.\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 \/ water separator\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003e100 hours or annually\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eReplace more often in ethanol fuel environments; check for water and debris.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-fuel-filters\"\u003eMerCruiser Fuel 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;\"\u003e200 hours or every 2 seasons\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eInspect annually; replace sooner if water stream weakens or overheat occurs.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-impellers\"\u003eMerCruiser Impellers\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eAnodes (sacrificial)\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eInspect every 50 hours; replace at ~50% wear\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eUse alloy matched to water type (zinc\/salt, aluminum\/brackish, magnesium\/fresh).\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-anodes\"\u003eMerCruiser Anodes\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"common-parts\"\u003e\n  \u003ch2\u003eFrequently Used Parts Categories\u003c\/h2\u003e\n  \u003cul\u003e\n    \u003cli\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/service-maintenance-kits\"\u003eRoutine Service Kits\u003c\/a\u003e\u003c\/li\u003e\n    \u003cli\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-impellers\"\u003eCooling System: Impellers\u003c\/a\u003e\u003c\/li\u003e\n    \u003cli\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-fuel-filters\"\u003eFuel System: Filters \u0026amp; Water Separators\u003c\/a\u003e\u003c\/li\u003e\n    \u003cli\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/electrical-items\"\u003eIgnition \/ Electrical\u003c\/a\u003e\u003c\/li\u003e\n    \u003cli\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-anodes\"\u003eCorrosion Protection (Anodes)\u003c\/a\u003e\u003c\/li\u003e\n    \u003cli\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/lower-unit-seal-kits\"\u003eLower Unit \u0026amp; Seals\u003c\/a\u003e\u003c\/li\u003e\n    \u003cli\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/propellers\"\u003ePropellers\u003c\/a\u003e\u003c\/li\u003e\n  \u003c\/ul\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"troubleshooting\"\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 tell‑tale stream or overheat alarm\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eInspect water intake screens for blockage; verify impeller age; check thermostat for sticking.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eWater pump kit, intake screen, thermostat\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;\"\u003eReplace fuel filter; inspect spark plugs; test compression; verify prop pitch\/condition.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eFuel filter, spark plugs, ignition components, propeller\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 (EFI)\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eCheck battery voltage; inspect injectors for clogging; look for vacuum leaks and stale fuel.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eBattery, fuel filter, injectors, hoses\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eGearcase noise or metal in gear oil\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eDrain oil and inspect; pressure\/vacuum test seals; verify prop shaft for fishing line damage.\u003c\/td\u003e\n        \u003ctd style=\"padding:8px; border-bottom:1px solid #f3f4f6;\"\u003eLower unit seals, bearings, 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\"\u003e\n  \u003ch2\u003eFAQs\u003c\/h2\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eAre parts interchangeable between different years or platforms?\u003c\/summary\u003e\n    \u003cp\u003eNot always. Cooling, ignition, fuel, and gearcase components can change by year, shaft length, and EFI vs. carbureted platforms. Confirm with your full model and 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\u003eAs preventive maintenance, replace every 200 hours or every two seasons. Replace sooner if the tell‑tale stream is weak, you overheat, or the engine ingested sand\/debris.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow often should the lower unit gear oil be changed?\u003c\/summary\u003e\n    \u003cp\u003eChange at least every 100 hours or once per year. If the oil appears milky or metallic, service immediately and pressure‑test the gearcase seals.\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\u003eProvide the engine’s model and serial number, shaft length, control type, and any visible option codes (e.g., saltwater package). Photos of the nameplate and the part needing replacement help verify fit.\u003c\/p\u003e\n  \u003c\/details\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"cta\" style=\"padding:16px; border:1px solid #e5e7eb; border-radius:8px;\"\u003e\n  \u003cp\u003eReady to find parts by horsepower, year, and model? Browse the main MerCruiser collection for GM‑based marine engines and refine using the Filter \u0026amp; Sort tools.\u003c\/p\u003e\n  \u003cp\u003e\n    \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser\" style=\"display:inline-block; padding:10px 16px; background:#0ea5e9; color:#fff; text-decoration:none; border-radius:6px;\"\u003eShop MerCruiser Collection\u003c\/a\u003e\n  \u003c\/p\u003e\n  \u003cp style=\"font-size:0.95em; color:#374151;\"\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\/gm-4-stroke-125hp-marine-engine-parts.oembed","provider":"SeaSierra","version":"1.0","type":"link"}