Thermostat for Nissan/Tohatsu Marine Outboards 3.5–40 HP, 50°C – Replaces 350-01030-1, 345-01030-1, 346-01030
Thermostat for Nissan/Tohatsu Marine Outboards 3.5–40 HP, 50°C – Replaces 350-01030-1, 345-01030-1, 346-01030 is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
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Thermostat for Nissan/Tohatsu Marine Outboards 3.5–40 HP, 50°C – Re...
Thermostat for Nissan/Tohatsu Marine Outboards 3.5–40 HP, 50°C – Replaces 350-01030-1, 345-01030-1, 346-01030 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket 50°C (122°F) thermostat is intended for selected Nissan and Tohatsu marine outboard applications. The company fitment range is listed as 3.5–40 HP, 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.
This thermostat is listed as a replacement for the following manufacturer references: 350-01030-1, 345-01030-1, 346-01030, and 346010320M. Additional catalog records identify 3H6-01030-0 as a thermostat reference used on selected Tohatsu MFS 2–6 HP four-stroke models.
- 50°C (122°F) thermostat specification.
- For selected Nissan and Tohatsu marine outboard motors.
- Suitable for applications across the company-listed 3.5–40 HP range, subject to exact model and part-number verification.
- Sold as one thermostat; gaskets, O-rings, seals, and other installation hardware are not confirmed as included unless shown in the product package received.
Part Number Matrix
Use 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.
| Brand or Reference | Part Number |
|---|---|
| Tohatsu | 350-01030-1 |
| Tohatsu | 345-01030-1 |
| Tohatsu / Nissan | 346-01030 |
| Catalog reference | 346010320M |
| Selected Tohatsu MFS applications | 3H6-01030-0 |
Engine & Model Compatibility
The 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.
| Brand | Model or Model Family | Rated HP | Stroke | Reference | Application Notes |
|---|---|---|---|---|---|
| Tohatsu | MFS2 / MFS2.5 / MFS3.5B | 2–3.5 | 4-Stroke | 3H6-01030-0 | Catalog-listed applications for selected model years. |
| Tohatsu | MFS4 / MFS5 / MFS6C | 4–6 | 4-Stroke | 3H6-01030-0 | Catalog-listed applications for selected model years. |
| Tohatsu | M6 / M8 / M9.8B | 6–9.8 | 2-Stroke | 350-01030-1 | Catalog-listed applications for selected model years. |
| Tohatsu | M9.9 / 15D2 / 18E2 | 9.9–18 | 2-Stroke | 350-01030-1 | Catalog-listed applications for selected model years. |
| Tohatsu | MX15 / MX18E2 | 15–18 | 2-Stroke | 350-01030-1 | Catalog-listed applications for selected model years. |
| Tohatsu | M25 / 30H / JET | 25–30 | 2-Stroke | 345-01030-1 | Catalog-listed applications for 2025–2026 model records. |
| Nissan / Tohatsu | Selected outboard models | 3.5–40 | Not specified | 350-01030-1, 345-01030-1, 346-01030 | Verify the exact model, year, serial range, and original thermostat reference. |
Technical Specifications
- Product Type
- Thermostat
- Temperature Rating
- 50°C (122°F)
- Application
- Selected Nissan and Tohatsu marine outboard motors
- Company-Listed Fitment Range
- 3.5–40 HP, with additional specific references to 2, 2.5, 3.5, 4, 5, and 6 HP applications
- Construction Material
- Not specified by the company catalog
- Installation Hardware
- Not specified; inspect the package contents before installation
What’s in the Box
- 1 × Thermostat
- Gasket, O-rings, seals, and other hardware are not confirmed as included.
Installation Notes
- Turn off the outboard, remove the ignition key, and allow the engine to cool completely.
- Disconnect the battery or follow the isolation procedure specified for your boat and engine.
- Locate the thermostat housing using the engine service manual.
- Remove the housing cover and note the original thermostat orientation before removal.
- Remove the old thermostat and inspect the housing, mating surfaces, gasket, and sealing components.
- Clean the mating surfaces without damaging the housing or cylinder-head sealing area.
- Install 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.
- Reinstall the housing cover and tighten the fasteners to the manufacturer’s specified torque.
- Restore the cooling-water supply, start the engine, and check for leaks and proper water flow during a controlled test.
- Stop the engine immediately if it overheats, leaks, or shows abnormal temperature behavior.
Troubleshooting & FAQ
What are the signs of a failing thermostat?
Possible 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.
How can I confirm this thermostat fits my engine?
Compare 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.
Is this a 50°C or 60°C thermostat?
This listing is for a 50°C (122°F) thermostat. Use only the temperature rating specified for your engine.
Is this a complete repair kit?
The 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.
Is this an OEM part?
This is an aftermarket replacement, not an original manufacturer component. The manufacturer part numbers shown are provided for identification and compatibility reference only.
What should I do if my model is not listed?
Check 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.
Shipping speed and cost
Standard shipping is free where offered. Typical transit is 5–15 days, while expedited options appear at checkout where available.
Warranty and returns
This 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.
Safety & Important Information
- Verify the exact engine application and thermostat temperature rating before purchase.
- Do not assume that every engine within the listed horsepower range uses the same thermostat.
- Do not operate the outboard without an adequate cooling-water supply.
- Allow the engine to cool before servicing the thermostat housing.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended when the correct procedure or torque specification is unknown.
About Sea Sierra
- Pro-Grade Standards — We supply marine replacement parts selected for dependable service in real-world conditions.
- Fast Global Fulfillment — Free standard delivery is available to most regions, with typical transit of 5–15 days.
- Manufacturer-Direct Value — Fair pricing and practical marine-part support.
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