{"title":"General Motors 4-Stroke 340HP Marine Engine Parts","description":"\u003csection id=\"hero\" style=\"padding:16px; border:1px solid #e5e7eb; border-radius:8px; max-width:980px;\"\u003e\n  \u003cp\u003eThis page is for General Motors 4-Stroke 340HP outboard engines. It helps you find compatible replacement parts and service information. Below you’ll find maintenance tips, common replacement parts, and troubleshooting guidance. You can also browse the main MerCruiser collection for GM-based marine engines. Scroll down to the bottom of the page to start browsing parts for this engine. On the collection page, use the “Filter \u0026amp; Sort” controls to narrow results by horsepower, year range, and part category\/section.\u003c\/p\u003e\n  \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser\" style=\"display:inline-block; margin-top:8px; padding:10px 14px; background:#0ea5e9; color:#fff; text-decoration:none; border-radius:6px;\"\u003eBrowse All MerCruiser Parts\u003c\/a\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"identify-model\" style=\"padding:16px; max-width:980px;\"\u003e\n  \u003ch2\u003eHow to Identify Your 340HP Model\u003c\/h2\u003e\n  \u003cul\u003e\n    \u003cli\u003eLocate the engine serial\/nameplate on or near the intake manifold, valve cover, or ECM bracket. A second tag may be on the bellhousing or near the transmission\/oil cooler bracket.\u003c\/li\u003e\n    \u003cli\u003eNote the marinizer (e.g., MerCruiser, PCM, Indmar, Volvo Penta). Model suffixes often indicate fuel system (MPI), calibration\/HP (e.g., 340), and cooling type (raw vs. closed).\u003c\/li\u003e\n    \u003cli\u003eRecord ECM information (calibration label) and rotation (LH is common) to match ignition, sensors, and harnesses.\u003c\/li\u003e\n    \u003cli\u003eCheck cooling layout and raw-water pump drive type (belt-driven, crank-driven, or serpentine) to select the correct impeller and hoses.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"engine-overview\" style=\"padding:16px; max-width:980px;\"\u003e\n  \u003ch2\u003ePlatform Overview\u003c\/h2\u003e\n  \u003ch3\u003eGM Small-Block V8 EFI 4‑Stroke (≈330–345 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:6px;\"\u003eFeature\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:6px;\"\u003eDescription\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eConfiguration\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003e90° V8 gasoline EFI (MPI\/MEFI) 4‑stroke, typically 5.7L\/6.0L with ECM‑controlled ignition and fuel.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eCommon Models\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eExamples include PCM Excalibur 5.7, MerCruiser 350 MAG MPI, and Indmar 340‑hp calibrations. Year range commonly early‑2000s through mid‑2010s.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eAdvantages\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eBroad torque curve, strong parts availability, proven reliability, good service access on most installations.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eNotes\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eMany external parts are marinizer‑specific (cooling, brackets, pumps, ECM harness). Match by serial\/model, cooling type (raw vs. closed), and raw‑water pump style (belt, crank, serpentine).\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=\"padding:16px; max-width:980px;\"\u003e\n  \u003ch2\u003eRoutine Maintenance \u0026amp; Service Parts\u003c\/h2\u003e\n  \u003cp\u003eIntervals below are general guidelines for 4‑stroke GM V8 marine engines. Always follow your specific marinizer’s official service manual and 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:6px;\"\u003eItem\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:6px;\"\u003eInterval*\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:6px;\"\u003eRemarks\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:6px;\"\u003eParts Link\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eEngine oil \u0026amp; filter\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eEvery 100 hours or annually\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eUse marine 4‑stroke oil (FC‑W) and a quality spin‑on filter; change sooner in harsh use.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-oil-filters\"\u003eMerCruiser Oil Filters\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eGear oil \/ transmission fluid\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eEvery 100 hours or annually\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eService sterndrive gear lube or inboard transmission fluid per marinizer spec.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-service-maintenance-kits\"\u003eMerCruiser Service \u0026amp; Maintenance Kits\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eSpark plugs\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eInspect 100 hours; replace 200 hours\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eGap and heat range per ECM calibration; replace sooner if fouled.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; 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:6px; border-bottom:1px solid #f3f4f6;\"\u003eFuel filter \/ water separator\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eEvery 100 hours or annually\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eDrain\/replace more often with ethanol fuel or contamination.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; 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:6px; border-bottom:1px solid #f3f4f6;\"\u003eRaw-water pump impeller\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003e1–2 seasons or 200 hours\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eReplace sooner after overheat, dry‑run, or long storage.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; 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:6px; border-bottom:1px solid #f3f4f6;\"\u003eAnodes (zinc\/aluminum\/magnesium)\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eInspect 50 hours; replace at 50% loss\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eMatch alloy to water type (salt\/brackish\/fresh) to protect cooling \u0026amp; exhaust hardware.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; 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      \u003ctr\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eSerpentine \/ drive belts\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eInspect 100 hours; replace if cracked\/noisy\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eCheck tensioner and idlers when replacing the belt.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/belt\"\u003eBelts\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\" style=\"padding:16px; max-width:980px;\"\u003e\n  \u003ch2\u003eFrequently Used Parts Categories\u003c\/h2\u003e\n  \u003cul\u003e\n    \u003cli\u003eRoutine Service: \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-service-maintenance-kits\"\u003eMerCruiser Service \u0026amp; Maintenance Kits\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eCooling System: \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-impellers\"\u003eImpellers\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 and \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-fuel-pumps\"\u003eFuel Pumps\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eIgnition \/ Sensors: \u003ca href=\"https:\/\/seasierra.com\/collections\/sensors\"\u003eSensors\u003c\/a\u003e and \u003ca href=\"https:\/\/seasierra.com\/collections\/spark-plug\"\u003eSpark Plugs\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eCharging \/ Starting: \u003ca href=\"https:\/\/seasierra.com\/collections\/alternators\"\u003eAlternators\u003c\/a\u003e and \u003ca href=\"https:\/\/seasierra.com\/collections\/starters\"\u003eStarters\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eGaskets \u0026amp; Manifolds: \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-gaskets\"\u003eGaskets\u003c\/a\u003e and \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-manifolds\"\u003eManifolds\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eCorrosion Protection: \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser-anodes\"\u003eAnodes\u003c\/a\u003e\n\u003c\/li\u003e\n  \u003c\/ul\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"troubleshooting\" style=\"padding:16px; max-width:980px;\"\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:6px;\"\u003eSymptom\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:6px;\"\u003eCheck First\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #e5e7eb; padding:6px;\"\u003eRelated Parts\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eWeak water flow or overheat alarm\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eInspect sea strainer\/intake screen, raw‑water pump impeller, hoses, and thermostat operation.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eWater pump impeller kit, hoses\/clamps, thermostat, anodes.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003ePoor acceleration \/ power loss\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eCheck fuel quality, water‑separating filter, anti‑siphon valve, and plug condition. Verify no exhaust restriction.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eFuel filter, fuel pump, injectors, spark plugs.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eHard starting \/ rough idle\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eBattery voltage\/grounds, IAC valve cleanliness, MAP sensor vacuum line, and vacuum leaks.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eSpark plugs, sensors (IAC\/MAP), fuel filter.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eCharging warning \/ low voltage\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eInspect belt condition\/tension, alternator output, and battery connections.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eAlternator, drive belt, battery cables.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eGear noise or metal in oil\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eVerify fluid level\/condition in sterndrive or transmission; inspect for water intrusion and magnet debris.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px; border-bottom:1px solid #f3f4f6;\"\u003eService kit, seals, cooler hoses\/fittings.\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=\"padding:16px; max-width:980px;\"\u003e\n  \u003ch2\u003eFAQs\u003c\/h2\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eAre parts interchangeable between different years or marinizers?\u003c\/summary\u003e\n    \u003cp\u003eInternal GM long‑block parts often interchange, but many external components (cooling system parts, brackets, ECM, harnesses, and pumps) are marinizer‑specific. Always match by serial\/model, cooling type, and pump style.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhen should I replace the raw‑water impeller?\u003c\/summary\u003e\n    \u003cp\u003eTypically every 1–2 seasons or ~200 hours. Replace immediately after any overheat, dry‑run, or long storage to prevent overheating and pump damage.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow often should gear oil or transmission fluid be changed?\u003c\/summary\u003e\n    \u003cp\u003eAs a rule of thumb, every 100 hours or annually, and any time contamination or water intrusion is suspected.\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 engine serial\/model, marinizer brand, cooling type (raw or closed), raw‑water pump drive (belt, crank, or serpentine), and any ECM calibration or rotation details on the label.\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:980px;\"\u003e\n  \u003cp\u003eReady to find parts? Browse the main MerCruiser collection to filter by horsepower, year, and model, then refine by category.\u003c\/p\u003e\n  \u003ca href=\"https:\/\/seasierra.com\/collections\/mercruiser\" style=\"display:inline-block; margin-top:8px; padding:10px 14px; background:#0ea5e9; color:#fff; text-decoration:none; border-radius:6px;\"\u003eBrowse All MerCruiser Parts\u003c\/a\u003e\n  \u003cp style=\"margin-top:8px; 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\/general-motors-4-stroke-340hp-marine-engine-parts.oembed","provider":"SeaSierra","version":"1.0","type":"link"}