Thermostat Kit, 50°C (122°F) – Fits Tohatsu/Nissan 2–50 HP Outboards
Thermostat Kit, 50°C (122°F) – Fits Tohatsu/Nissan 2–50 HP Outboards is backordered and will ship as soon as it is back in stock.
Worry-free returns
Worry-free returns
Shop with confidence. If you’re not completely satisfied, eligible items may be returned within the return window, provided they are unused and in original packaging.
If the return is due to our error or a defective item, we’ll make it right.
Please contact us before returning any item.
Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
U.S. orders usually arrive within 6–15 days, depending on stock location and destination.
International delivery times may vary due to customs processing.
Tracking information will be provided once your order ships.
Thermostat Kit, 50°C (122°F) – Fits Tohatsu/Nissan 2–50 HP Outboards
Thermostat Kit, 50°C (122°F) – Fits Tohatsu/Nissan 2–50 HP Outboards is backordered and will ship as soon as it is back in stock.
Product Details
This 50°C (122°F) thermostat kit is an aftermarket replacement for selected Tohatsu and Nissan outboard motors. It is intended to help the cooling system maintain the engine's specified operating temperature and includes the service components needed for a thermostat replacement.
The kit is associated with Tohatsu/Nissan thermostat references including 345-01030-0, 345-01030-1, 346-01030-0, 346-01030-1, 350-01030-1, and 3H6-01030-0. Reference numbers are provided for identification; always confirm the exact model, year, stroke, and serial-number range before ordering.
- 50°C (122°F) thermostat rating.
- Kit format for thermostat service.
- Includes a thermostat, housing gasket, and thermostat seals.
- For selected Tohatsu and Nissan 2-stroke and 4-stroke outboards.
Part Number Matrix
Use the following manufacturer reference numbers when comparing your original part and engine parts diagram.
| Brand | Manufacturer Reference |
|---|---|
| Tohatsu / Nissan | 345-01030-0 |
| Tohatsu / Nissan | 345-01030-1 |
| Tohatsu / Nissan | 346-01030-0 |
| Tohatsu / Nissan | 346-01030-1 |
| Tohatsu / Nissan | 350-01030-1 |
| Tohatsu / Nissan | 3H6-01030-0 |
Verified Engine Compatibility Examples
The catalog relationships below keep the model, horsepower, stroke, and year conditions together. They are examples of documented applications, not a substitute for checking the complete engine identification and serial-number information.
| Brand | Model or Model Group | Rated HP | Stroke | Year Evidence | Reference |
|---|---|---|---|---|---|
| Tohatsu | M6 / M8 / M9.8B | 6–9.8 | 2-Stroke | 2013–2016 catalog examples | 350-01030-1 |
| Tohatsu | M9.9 / 15D2 / 18E2 / MX18E2 | 9.9–18 | 2-Stroke | 2013–2015 catalog examples | 350-01030-1 |
| Tohatsu | M25/30H/JET | 25–30 | 2-Stroke | 2025–2026 catalog examples | 345-01030-1 |
| Tohatsu | MX25/30H | 25–30 | 2-Stroke | 2025–2026 catalog examples | 345-01030-1 |
| Tohatsu | MFS2 / MFS2.5 / MFS3.5B | 2–3.5 | 4-Stroke | 2013–2017 catalog examples | 3H6-01030-0 |
| Tohatsu | MFS4 / MFS5 / MFS6C | 4–6 | 4-Stroke | 2013–2017 catalog examples | 3H6-01030-0 |
Additional applications may exist under the reference numbers above. Model names, production years, and serial-number ranges can vary by market and engine revision, so verify against the engine's identification plate and the applicable parts diagram.
Technical Specifications
- Product Type
- Thermostat kit
- Thermostat Rating
- 50°C (122°F)
- Application
- Selected Tohatsu and Nissan 2-stroke and 4-stroke outboard motors
- Installation
- Replacement installation using the original thermostat housing
- Included Components
- Thermostat, housing gasket, and thermostat seals
- Product Status
- Aftermarket replacement; not an OEM-branded component
What's in the Box
- 1x 50°C (122°F) thermostat
- 1x thermostat housing gasket
- 2x thermostat seals
Installation Notes
- Allow the engine to cool completely before beginning work. Follow the engine manufacturer's safety procedures.
- Locate the thermostat housing and place a suitable drain pan below the work area to collect water or coolant released during disassembly.
- Remove the housing cover carefully and note the orientation of the old thermostat, gasket, and seals.
- Clean the mating surfaces and remove old gasket material without damaging the housing or cover.
- Install the new thermostat in the same orientation as the original, then fit the supplied gasket and seals.
- Reinstall the housing cover and tighten the fasteners evenly to the manufacturer's specified torque.
- Restore the cooling system as required for the engine, run the outboard according to the service instructions, and check for leaks and normal water flow.
Do not substitute automotive coolant procedures for the outboard manufacturer's service procedure. Use the correct fluid and bleeding or flushing method for your specific engine.
Troubleshooting & FAQ
What are common signs of a failed thermostat?
Possible symptoms include overheating, unusually low operating temperature, inconsistent temperature behavior, or poor cooling-system performance. Blocked water passages, a damaged water pump, or other cooling-system faults can cause similar symptoms.
What temperature is this thermostat rated for?
This kit is listed with a 50°C (122°F) thermostat rating.
How do I confirm fitment?
Compare your original manufacturer reference with the Part Number Matrix, then verify the engine brand, exact model, horsepower, stroke, production year, and serial-number range in the applicable parts diagram. Do not rely on horsepower alone.
Does the kit include the service gaskets and seals?
Yes. The listed kit contents are one thermostat, one thermostat housing gasket, and two thermostat seals.
Is this an OEM part?
No. This is an aftermarket replacement kit intended for the documented manufacturer reference numbers and applications listed on this page.
Is there a fixed replacement interval?
Follow the maintenance schedule for your specific outboard. Inspect the thermostat when diagnosing cooling-system problems or when the thermostat housing is opened for related service.
Safety & Important Information
- Work only on a cool engine and follow the manufacturer's service and safety instructions.
- Confirm the exact model, year, stroke, and serial-number range before purchase.
- Compare the supplied part and sealing components with the original before installation.
- Professional installation is recommended when the correct procedure or torque specifications are unavailable.
- This is an aftermarket replacement, not an OEM-branded component.
About Sea Sierra
- Marine replacement parts selected for documented applications and practical service needs.
- Clear reference-number and fitment information to help support accurate part selection.
- Customer support is available for installation and fitment questions when complete engine details are provided.
Payment & Security
Payment methods
Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.
