{"title":"Tohatsu 4-Stroke 3.5-40HP Outboard Engine Parts","description":"\u003csection id=\"hero\" style=\"padding:16px; max-width:980px; margin:auto;\"\u003e\n  \u003cp\u003eThis page is tailored for Tohatsu 4-Stroke 3.5–40HP outboard engines. Use it to find compatible parts and practical service information. Below you’ll find maintenance tips, common replacement parts, and troubleshooting guidance. You can also browse the main Tohatsu collection at any time. 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  \u003ca href=\"https:\/\/seasierra.com\/collections\/tohatsu-outboard-parts\" style=\"display:inline-block; padding:10px 16px; background:#0b5; color:#fff; text-decoration:none; border-radius:6px;\"\u003eBrowse All Tohatsu Parts\u003c\/a\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"identify-model\" style=\"padding:16px; max-width:980px; margin:auto;\"\u003e\n  \u003ch2\u003eHow to Identify Your 3.5–40HP Model\u003c\/h2\u003e\n  \u003cul\u003e\n    \u003cli\u003eLocate the nameplate\/serial sticker on the transom bracket or steering swivel. It lists the model designation and serial number needed for parts lookup.\u003c\/li\u003e\n    \u003cli\u003eDecode the suffixes: shaft length (e.g., S\/L\/XL), tiller vs. remote control, and electric vs. manual start. These options affect cables, harnesses, and prop\/hub selection.\u003c\/li\u003e\n    \u003cli\u003eConfirm platform: small portable models (3.5–6HP) are typically single-cylinder; 8–20HP are commonly twin-cylinder; 25–40HP are inline-3 mid‑range. Platform differences change items like ignition, fuel, and cooling components.\u003c\/li\u003e\n    \u003cli\u003eFor 4‑stroke models, check the engine‑oil service label and oil fill\/dipstick location to verify the engine family and maintenance needs.\u003c\/li\u003e\n  \u003c\/ul\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"engine-overview\" style=\"padding:16px; max-width:980px; margin:auto;\"\u003e\n  \u003ch2\u003eEngine Overview\u003c\/h2\u003e\n\n  \u003ch3\u003ePortable Single-Cylinder (Approx. 3.5–6HP)\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 #ddd;\"\u003eFeature\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #ddd;\"\u003eDescription\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eConfiguration\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eSingle-cylinder, carbureted 4‑stroke portable outboards.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eCommon Models\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003e3.5–6HP 4‑stroke portable models.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eAdvantages\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eLightweight, simple maintenance, excellent portability.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eNotes\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eSome engines use an internal oil screen instead of a spin‑on filter. Verify model\/serial for correct impeller and gearcase seals.\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\n  \u003ch3\u003ePortable Twin-Cylinder (Approx. 8–20HP)\u003c\/h3\u003e\n  \u003ctable style=\"width:100%; border-collapse:collapse; margin-top:10px;\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #ddd;\"\u003eFeature\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #ddd;\"\u003eDescription\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eConfiguration\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eTwin‑cylinder 4‑stroke; carbureted or EFI depending on year\/variant.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eCommon Models\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003e8–20HP 4‑stroke portable models (tiller or remote).\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eAdvantages\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eSmooth running, good charging (on electric‑start variants), versatile for small boats.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eNotes\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eFuel and ignition parts vary by carb\/EFI. Water pump and seal kits depend on gearcase version and shaft length; confirm by model code.\u003c\/td\u003e\n      \u003c\/tr\u003e\n    \u003c\/tbody\u003e\n  \u003c\/table\u003e\n\n  \u003ch3\u003eMid‑Range Inline‑3 (Approx. 25–40HP)\u003c\/h3\u003e\n  \u003ctable style=\"width:100%; border-collapse:collapse; margin-top:10px;\"\u003e\n    \u003cthead\u003e\n      \u003ctr\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #ddd;\"\u003eFeature\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #ddd;\"\u003eDescription\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eConfiguration\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eInline‑3 4‑stroke, commonly EFI with improved torque and economy.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eCommon Models\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003e25–40HP mid‑range 4‑stroke models.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eAdvantages\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eSmoother operation, stronger mid‑range pull, better alternator output.\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eNotes\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eEFI fuel filters and thermostats are model‑specific. Many cooling and gearcase parts differ from portable families—verify by model\/serial.\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; margin:auto;\"\u003e\n  \u003ch2\u003eRoutine Maintenance \u0026amp; Service Parts\u003c\/h2\u003e\n  \u003cp\u003eIntervals below are general guidelines for typical recreational use. Always follow the official service manual for your exact model and 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 #ddd;\"\u003eItem\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #ddd;\"\u003eInterval*\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #ddd;\"\u003eRemarks\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #ddd;\"\u003eParts Link\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eEngine oil + filter (4‑stroke)\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003e100 hrs or annually\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eUse FC‑W marine oil. Some portable models use an oil screen instead of a spin‑on filter—check your manual.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/oil-filters\"\u003eOil Filters\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eGear oil (lower unit)\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003e100 hrs or annually\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eChange after break‑in and any impact\/grounding. Inspect for milkiness (water intrusion).\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/tohatsu-lower-unit-seal-kits\"\u003eTohatsu Lower Unit Seal Kits\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eSpark plugs\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eInspect 100 hrs; replace as needed\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eCheck gap and insulator color; replace if fouled or worn.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\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 0;\"\u003eInline fuel filter\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003e100 hrs or seasonally\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eShorten interval with ethanol fuel or dirty tanks. EFI models may have additional fine filters.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\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 0;\"\u003eWater pump impeller\/kit\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003e2–3 seasons or 200 hrs\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eReplace sooner for sandy\/silty use or weak tell‑tale stream.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/tohatsu-water-pump-repair-kits\"\u003eTohatsu Water Pump Repair Kits\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eAnodes (sacrificial)\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eInspect 50 hrs or monthly in saltwater\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eReplace when ~50% consumed. Match alloy (aluminum, zinc, magnesium) to water type.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/anodes\"\u003eAnodes\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eThermostat\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eInspect 200 hrs or if overheat\/slow warm‑up\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eReplace if corroded or sticking. Use correct temp rating for the model.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/tohatsu-outboard-parts\"\u003eTohatsu Outboard Parts\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003ePropeller \u0026amp; cotter\/hardware\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eInspect every trip\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eRemove fishing line from shaft; check hub condition; replace cotter pins when removed.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/propellers\"\u003ePropellers\u003c\/a\u003e\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eCharging\/rectifier checks (electric‑start models)\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eAnnually\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eVerify output voltage and inspect connectors\/fuses.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003e\u003ca href=\"https:\/\/seasierra.com\/collections\/electrical-items\"\u003eElectrical Items\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:#555;\"\u003e*Always consult your official Tohatsu service manual for precise intervals and specifications.\u003c\/p\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"common-parts\" style=\"padding:16px; max-width:980px; margin:auto;\"\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\/tohatsu-water-pump-repair-kits\"\u003eTohatsu Water Pump Repair Kits\u003c\/a\u003e\n\u003c\/li\u003e\n    \u003cli\u003eGearcase Seals — \u003ca href=\"https:\/\/seasierra.com\/collections\/tohatsu-lower-unit-seal-kits\"\u003eTohatsu Lower Unit Seal 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\u003ePropellers \u0026amp; Hardware — \u003ca href=\"https:\/\/seasierra.com\/collections\/propellers\"\u003ePropellers\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  \u003c\/ul\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"troubleshooting\" style=\"padding:16px; max-width:980px; margin:auto;\"\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 #ddd;\"\u003eSymptom\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #ddd;\"\u003eCheck First\u003c\/th\u003e\n        \u003cth style=\"text-align:left; border-bottom:1px solid #ddd;\"\u003eRelated Parts\u003c\/th\u003e\n      \u003c\/tr\u003e\n    \u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eWeak tell‑tale stream or overheat alarm\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eInspect intake screen for debris; test impeller condition; verify thermostat operation; flush system after silty use.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eWater pump kit, thermostat, intake screen, anodes\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eHard starting or rough idle\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eConfirm fresh fuel; squeeze primer bulb; check choke\/fast‑idle; inspect spark plug gap\/condition.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eSpark plugs, fuel filter, carburetor repair kit, EFI filter\/injector service (EFI models)\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003ePoor acceleration or power loss\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eCheck prop for damage or wrong pitch; look for air leaks at fuel connectors; verify timing\/ECU codes; clean VST\/jetting as applicable.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003ePropeller, fuel pump, fuel filter, ignition coil\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eGearcase noise or metal in gear oil\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eCheck oil level\/condition; inspect prop shaft for fishing line; pressure\/vacuum test seals after any impact.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eGearcase seals, bearings, water pump key, gear oil\u003c\/td\u003e\n      \u003c\/tr\u003e\n      \u003ctr\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eBattery not charging (electric‑start)\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eTest fuses and connectors; measure rectifier\/regulator output; check stator charge coil resistance.\u003c\/td\u003e\n        \u003ctd style=\"padding:6px 0;\"\u003eRectifier\/regulator, alternator\/stator, wiring\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; margin:auto;\"\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\u003eSome wear items may interchange within the same family, but changes in platform (single\/twin\/inline‑3), EFI vs. carbureted fuel systems, and control options often require specific parts. Verify by model designation and serial number before ordering.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eWhen should the impeller be replaced?\u003c\/summary\u003e\n    \u003cp\u003eAs a rule, every 2–3 seasons or about 200 hours, and sooner if you operate in sand\/silt or see a weak tell‑tale stream or overheat warnings. Replace the full water pump kit when housing wear is suspected.\u003c\/p\u003e\n  \u003c\/details\u003e\n  \u003cdetails\u003e\n    \u003csummary\u003eHow often should the gear oil be changed?\u003c\/summary\u003e\n    \u003cp\u003eChange at 100 hours or annually, and immediately after any impact or if water contamination (milky oil) is detected. Inspect the magnetic drain plug for metal shavings.\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 full model code, serial number, shaft length (S\/L\/XL), starting method (manual\/electric), and control type (tiller\/remote). Photos of the nameplate and the existing part help ensure a precise match.\u003c\/p\u003e\n  \u003c\/details\u003e\n\u003c\/section\u003e\n\n\u003csection id=\"cta\" style=\"padding:16px; max-width:980px; margin:auto;\"\u003e\n  \u003cp\u003eReady to find parts by horsepower, year, and model? Browse the main Tohatsu collection to get started.\u003c\/p\u003e\n  \u003ca href=\"https:\/\/seasierra.com\/collections\/tohatsu-outboard-parts\" style=\"display:inline-block; padding:10px 16px; background:#0b5; color:#fff; text-decoration:none; border-radius:6px;\"\u003eShop Tohatsu Outboard Parts\u003c\/a\u003e\n  \u003cp style=\"margin-top:8px; color:#555; font-size:12px;\"\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":[{"product_id":"thermostat-fits-tohatsu-nissan-3-5hp-40hp-replaces-350-01030-346-01030-3h6-01030-0","title":"Thermostat for Nissan\/Tohatsu Marine Outboards 3.5–40 HP, 50°C – Replaces 350-01030-1, 345-01030-1, 346-01030","description":"\u003csection\u003e\n\u003cstyle\u003e\n  .ss-table-wrap { overflow-x:auto; -webkit-overflow-scrolling:touch; }\n  table.ss-table { width:100%; border-collapse:collapse; min-width:640px; }\n  table.ss-table th, table.ss-table td { padding:10px 12px; border:1px solid #e5e7eb; text-align:left; vertical-align:top; }\n  table.ss-table th { white-space:nowrap; word-break:normal; letter-spacing:normal; font-weight:600; background:#f8fafc; }\n  @media (max-width:480px){ table.ss-table th, table.ss-table td { padding:8px 10px; font-size:14px; } }\n\u003c\/style\u003e\n\n\u003ch2\u003eProduct Details\u003c\/h2\u003e\n\u003cp\u003eThis aftermarket \u003cstrong\u003e50°C (122°F) thermostat\u003c\/strong\u003e is intended for selected Nissan and Tohatsu marine outboard applications. The company fitment range is listed as \u003cstrong\u003e3.5–40 HP\u003c\/strong\u003e, with specific small-engine references including 2, 2.5, 3.5, 4, 5, and 6 HP applications. Always match the thermostat specification and part number to your exact engine before ordering.\u003c\/p\u003e\n\u003cp\u003eThis thermostat is listed as a replacement for the following manufacturer references: \u003cstrong\u003e350-01030-1\u003c\/strong\u003e, \u003cstrong\u003e345-01030-1\u003c\/strong\u003e, \u003cstrong\u003e346-01030\u003c\/strong\u003e, and \u003cstrong\u003e346010320M\u003c\/strong\u003e. Additional catalog records identify \u003cstrong\u003e3H6-01030-0\u003c\/strong\u003e as a thermostat reference used on selected Tohatsu MFS 2–6 HP four-stroke models.\u003c\/p\u003e\n\u003cul\u003e\n  \u003cli\u003e50°C (122°F) thermostat specification.\u003c\/li\u003e\n  \u003cli\u003eFor selected Nissan and Tohatsu marine outboard motors.\u003c\/li\u003e\n  \u003cli\u003eSuitable for applications across the company-listed 3.5–40 HP range, subject to exact model and part-number verification.\u003c\/li\u003e\n  \u003cli\u003eSold as one thermostat; gaskets, O-rings, seals, and other installation hardware are not confirmed as included unless shown in the product package received.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003ePart Number Matrix\u003c\/h2\u003e\n\u003cp\u003eUse the references below to compare your original thermostat and service-manual information. Part-number matching is recommended because horsepower ranges can overlap between different engine families.\u003c\/p\u003e\n\u003cdiv class=\"ss-table-wrap\"\u003e\n  \u003ctable class=\"ss-table\" aria-label=\"Part Number Matrix\"\u003e\n    \u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eBrand or Reference\u003c\/th\u003e\n\u003cth\u003ePart Number\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n\u003ctd\u003eTohatsu\u003c\/td\u003e\n\u003ctd\u003e350-01030-1\u003c\/td\u003e\n\u003c\/tr\u003e\n      \u003ctr\u003e\n\u003ctd\u003eTohatsu\u003c\/td\u003e\n\u003ctd\u003e345-01030-1\u003c\/td\u003e\n\u003c\/tr\u003e\n      \u003ctr\u003e\n\u003ctd\u003eTohatsu \/ Nissan\u003c\/td\u003e\n\u003ctd\u003e346-01030\u003c\/td\u003e\n\u003c\/tr\u003e\n      \u003ctr\u003e\n\u003ctd\u003eCatalog reference\u003c\/td\u003e\n\u003ctd\u003e346010320M\u003c\/td\u003e\n\u003c\/tr\u003e\n      \u003ctr\u003e\n\u003ctd\u003eSelected Tohatsu MFS applications\u003c\/td\u003e\n\u003ctd\u003e3H6-01030-0\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\u003eThe company lists this thermostat for Nissan and Tohatsu marine outboards from 3.5 to 40 HP and separately references 2, 2.5, 3.5, 4, 5, and 6 HP applications. The catalog examples below document selected applications for the listed manufacturer references; they are not a complete model-year or serial-number list.\u003c\/p\u003e\n\u003cdiv class=\"ss-table-wrap\"\u003e\n  \u003ctable class=\"ss-table\" aria-label=\"Engine and Model Compatibility\"\u003e\n    \u003cthead\u003e\u003ctr\u003e\n\u003cth\u003eBrand\u003c\/th\u003e\n\u003cth\u003eModel or Model Family\u003c\/th\u003e\n\u003cth\u003eRated HP\u003c\/th\u003e\n\u003cth\u003eStroke\u003c\/th\u003e\n\u003cth\u003eReference\u003c\/th\u003e\n\u003cth\u003eApplication Notes\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n    \u003ctbody\u003e\n      \u003ctr\u003e\n\u003ctd\u003eTohatsu\u003c\/td\u003e\n\u003ctd\u003eMFS2 \/ MFS2.5 \/ MFS3.5B\u003c\/td\u003e\n\u003ctd\u003e2–3.5\u003c\/td\u003e\n\u003ctd\u003e4-Stroke\u003c\/td\u003e\n\u003ctd\u003e3H6-01030-0\u003c\/td\u003e\n\u003ctd\u003eCatalog-listed applications for selected model years.\u003c\/td\u003e\n\u003c\/tr\u003e\n      \u003ctr\u003e\n\u003ctd\u003eTohatsu\u003c\/td\u003e\n\u003ctd\u003eMFS4 \/ MFS5 \/ MFS6C\u003c\/td\u003e\n\u003ctd\u003e4–6\u003c\/td\u003e\n\u003ctd\u003e4-Stroke\u003c\/td\u003e\n\u003ctd\u003e3H6-01030-0\u003c\/td\u003e\n\u003ctd\u003eCatalog-listed applications for selected model years.\u003c\/td\u003e\n\u003c\/tr\u003e\n      \u003ctr\u003e\n\u003ctd\u003eTohatsu\u003c\/td\u003e\n\u003ctd\u003eM6 \/ M8 \/ M9.8B\u003c\/td\u003e\n\u003ctd\u003e6–9.8\u003c\/td\u003e\n\u003ctd\u003e2-Stroke\u003c\/td\u003e\n\u003ctd\u003e350-01030-1\u003c\/td\u003e\n\u003ctd\u003eCatalog-listed applications for selected model years.\u003c\/td\u003e\n\u003c\/tr\u003e\n      \u003ctr\u003e\n\u003ctd\u003eTohatsu\u003c\/td\u003e\n\u003ctd\u003eM9.9 \/ 15D2 \/ 18E2\u003c\/td\u003e\n\u003ctd\u003e9.9–18\u003c\/td\u003e\n\u003ctd\u003e2-Stroke\u003c\/td\u003e\n\u003ctd\u003e350-01030-1\u003c\/td\u003e\n\u003ctd\u003eCatalog-listed applications for selected model years.\u003c\/td\u003e\n\u003c\/tr\u003e\n      \u003ctr\u003e\n\u003ctd\u003eTohatsu\u003c\/td\u003e\n\u003ctd\u003eMX15 \/ MX18E2\u003c\/td\u003e\n\u003ctd\u003e15–18\u003c\/td\u003e\n\u003ctd\u003e2-Stroke\u003c\/td\u003e\n\u003ctd\u003e350-01030-1\u003c\/td\u003e\n\u003ctd\u003eCatalog-listed applications for selected model years.\u003c\/td\u003e\n\u003c\/tr\u003e\n      \u003ctr\u003e\n\u003ctd\u003eTohatsu\u003c\/td\u003e\n\u003ctd\u003eM25 \/ 30H \/ JET\u003c\/td\u003e\n\u003ctd\u003e25–30\u003c\/td\u003e\n\u003ctd\u003e2-Stroke\u003c\/td\u003e\n\u003ctd\u003e345-01030-1\u003c\/td\u003e\n\u003ctd\u003eCatalog-listed applications for 2025–2026 model records.\u003c\/td\u003e\n\u003c\/tr\u003e\n      \u003ctr\u003e\n\u003ctd\u003eNissan \/ Tohatsu\u003c\/td\u003e\n\u003ctd\u003eSelected outboard models\u003c\/td\u003e\n\u003ctd\u003e3.5–40\u003c\/td\u003e\n\u003ctd\u003eNot specified\u003c\/td\u003e\n\u003ctd\u003e350-01030-1, 345-01030-1, 346-01030\u003c\/td\u003e\n\u003ctd\u003eVerify the exact model, year, serial range, and original thermostat reference.\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\u003cdl\u003e\n  \u003cdt\u003eProduct Type\u003c\/dt\u003e\n  \u003cdd\u003eThermostat\u003c\/dd\u003e\n  \u003cdt\u003eTemperature Rating\u003c\/dt\u003e\n  \u003cdd\u003e50°C (122°F)\u003c\/dd\u003e\n  \u003cdt\u003eApplication\u003c\/dt\u003e\n  \u003cdd\u003eSelected Nissan and Tohatsu marine outboard motors\u003c\/dd\u003e\n  \u003cdt\u003eCompany-Listed Fitment Range\u003c\/dt\u003e\n  \u003cdd\u003e3.5–40 HP, with additional specific references to 2, 2.5, 3.5, 4, 5, and 6 HP applications\u003c\/dd\u003e\n  \u003cdt\u003eConstruction Material\u003c\/dt\u003e\n  \u003cdd\u003eNot specified by the company catalog\u003c\/dd\u003e\n  \u003cdt\u003eInstallation Hardware\u003c\/dt\u003e\n  \u003cdd\u003eNot specified; inspect the package contents before installation\u003c\/dd\u003e\n\u003c\/dl\u003e\n\n\u003ch2\u003eWhat’s in the Box\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e1 × Thermostat\u003c\/li\u003e\n  \u003cli\u003eGasket, O-rings, seals, and other hardware are not confirmed as included.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eInstallation Notes\u003c\/h2\u003e\n\u003col\u003e\n  \u003cli\u003eTurn off the outboard, remove the ignition key, and allow the engine to cool completely.\u003c\/li\u003e\n  \u003cli\u003eDisconnect the battery or follow the isolation procedure specified for your boat and engine.\u003c\/li\u003e\n  \u003cli\u003eLocate the thermostat housing using the engine service manual.\u003c\/li\u003e\n  \u003cli\u003eRemove the housing cover and note the original thermostat orientation before removal.\u003c\/li\u003e\n  \u003cli\u003eRemove the old thermostat and inspect the housing, mating surfaces, gasket, and sealing components.\u003c\/li\u003e\n  \u003cli\u003eClean the mating surfaces without damaging the housing or cylinder-head sealing area.\u003c\/li\u003e\n  \u003cli\u003eInstall the new thermostat in the correct orientation. Use a new gasket or seal only if required by the service manual and available for your application.\u003c\/li\u003e\n  \u003cli\u003eReinstall the housing cover and tighten the fasteners to the manufacturer’s specified torque.\u003c\/li\u003e\n  \u003cli\u003eRestore the cooling-water supply, start the engine, and check for leaks and proper water flow during a controlled test.\u003c\/li\u003e\n  \u003cli\u003eStop the engine immediately if it overheats, leaks, or shows abnormal temperature behavior.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003ch2\u003eTroubleshooting \u0026amp; FAQ\u003c\/h2\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWhat are the signs of a failing thermostat?\u003c\/summary\u003e\n  \u003cp\u003ePossible symptoms include overheating, unusually slow warm-up, unstable operating temperature, or temperature behavior that differs from the engine service-manual specification. Cooling-system blockages, water-pump problems, sensors, and incorrect installation can cause similar symptoms.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eHow can I confirm this thermostat fits my engine?\u003c\/summary\u003e\n  \u003cp\u003eCompare the original thermostat and service-manual part number with the references listed above. Confirm the exact engine model, horsepower, stroke, model year, and serial-number range where applicable. Do not rely on horsepower alone.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eIs this a 50°C or 60°C thermostat?\u003c\/summary\u003e\n  \u003cp\u003eThis listing is for a \u003cstrong\u003e50°C (122°F)\u003c\/strong\u003e thermostat. Use only the temperature rating specified for your engine.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eIs this a complete repair kit?\u003c\/summary\u003e\n  \u003cp\u003eThe company record for this product identifies it as a single thermostat rather than a multi-component kit. Only one thermostat is confirmed. Gaskets, O-rings, and other service parts are not confirmed as included.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eIs this an OEM part?\u003c\/summary\u003e\n  \u003cp\u003eThis is an aftermarket replacement, not an original manufacturer component. The manufacturer part numbers shown are provided for identification and compatibility reference only.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWhat should I do if my model is not listed?\u003c\/summary\u003e\n  \u003cp\u003eCheck the original thermostat number and your engine service manual. Contact support with the complete engine model, horsepower, stroke, year, and serial number before ordering if the application is unclear.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eShipping speed and cost\u003c\/summary\u003e\n  \u003cp\u003eStandard shipping is free where offered. Typical transit is 5–15 days, while expedited options appear at checkout where available.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n  \u003csummary\u003eWarranty and returns\u003c\/summary\u003e\n  \u003cp\u003eThis product is covered by a 1-year warranty against manufacturing defects under normal use. Returns are accepted within the standard return window when the item is unused and in its original condition. Contact support for instructions.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003ch2\u003eSafety \u0026amp; Important Information\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003eVerify the exact engine application and thermostat temperature rating before purchase.\u003c\/li\u003e\n  \u003cli\u003eDo not assume that every engine within the listed horsepower range uses the same thermostat.\u003c\/li\u003e\n  \u003cli\u003eDo not operate the outboard without an adequate cooling-water supply.\u003c\/li\u003e\n  \u003cli\u003eAllow the engine to cool before servicing the thermostat housing.\u003c\/li\u003e\n  \u003cli\u003eThis is an aftermarket replacement, not an OEM component.\u003c\/li\u003e\n  \u003cli\u003eProfessional installation is recommended when the correct procedure or torque specification is unknown.\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 replacement parts selected for dependable service in real-world conditions.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eFast Global Fulfillment\u003c\/strong\u003e — Free standard delivery is available to most regions, with typical transit of 5–15 days.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eManufacturer-Direct Value\u003c\/strong\u003e — Fair pricing and practical marine-part support.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/section\u003e","brand":"SeaSierra","offers":[{"title":"Default Title","offer_id":50723963732283,"sku":"23TH616","price":26.4,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0826\/8673\/8747\/files\/23TH616_1_1f99fe24-5742-4094-b080-b914a992ae26.jpg?v=1763038510"}],"url":"https:\/\/seasierra.com\/collections\/tohatsu-4-stroke-3-5-40hp-outboard-engine-parts.oembed","provider":"SeaSierra","version":"1.0","type":"link"}