Thermostat Kit (122°F/50°C) – Fits Tohatsu/Nissan 2–50 HP (Replaces 345-01030-0, 346-01030-0)

$21.99 $35.00

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Thermostat Kit (122°F/50°C) – Fits Tohatsu/Nissan 2–50 HP (Replaces 345-01030-0, 346-01030-0) is backordered and will ship as soon as it is back in stock.

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You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).

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Delivery and Shipping

Free standard shipping on all orders under 1 KG

If you have any questions, feel free to email us at info@sierramarines.com, and we’ll get back to you within 20–36 hours.

Product Details

This replacement Thermostat Kit (122°F/50°C) – Fits Tohatsu/Nissan 2–50 HP is engineered to regulate engine temperature for a wide range of Tohatsu and Nissan 2-stroke and 4-stroke outboard engines. It covers various models from approximately 2001 to 2014, including the M, MD, MF, and MFS series, ensuring your engine operates within its optimal temperature range for performance and longevity.

This kit serves as a direct interchange for Tohatsu part numbers 345-01030-0, 345010300M, 345010301M, 346-01030-0, 346-01030-1, 350-01030-1, and 3H6-01030-0.

Designed for direct OEM replacement, requiring no modifications for installation.
Maintains engine operating temperature at a consistent 122°F (50°C).
Includes the thermostat, housing gasket, and seals for a complete service.

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Brand	Part Number
Tohatsu	345-01030-0
Tohatsu	345010300M
Tohatsu	345010301M
Tohatsu	346-01030-0
Tohatsu	346-01030-1
Tohatsu	350-01030-1
Tohatsu	3H6-01030-0

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For Tohatsu engines, this part fits a broad range of 2-stroke and 4-stroke models from 2 HP to 50 HP. Please verify your specific model and OEM part number.

For Nissan outboards, this part fits corresponding 2-stroke and 4-stroke TLDI models. Ensure your part number matches the references.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.
Tohatsu	MFS2	2	4-Stroke		345-01030-0
Tohatsu	MFS2.5	2.5	4-Stroke		345-01030-0
Tohatsu	MFS3.5C	3.5	4-Stroke		345-01030-0
Tohatsu	MFS5	5	4-Stroke		345-01030-0
Tohatsu	MF6	6	4-Stroke	2006	345-01030-0
Tohatsu	M8B	8	2-Stroke		345-01030-0
Tohatsu	M9.8B	9.8	2-Stroke		345-01030-0
Tohatsu	M9.9D2	9.9	2-Stroke		345-01030-0
Tohatsu	M15D2	15	2-Stroke		345-01030-0
Tohatsu	M18E2	18	2-Stroke		345-01030-0
Tohatsu	M25C3	25	2-Stroke	2003	345-01030-0
Tohatsu	M30A4	30	2-Stroke	2003	345-01030-0
Tohatsu	M40C	40	2-Stroke	2004	345-01030-0
Tohatsu	MD40A, MD40B, MD40B2	40	4-Stroke TLDI	2010–2014	345010300M
Tohatsu	MD50A, MD50B, MD50B2	50	4-Stroke TLDI	2010–2014	345010300M
Nissan	NS25C3	25	2-Stroke	2003	345-01030-0
Nissan	NS30A4	30	2-Stroke	2003	345-01030-0
Nissan	NS40C	40	2-Stroke	2004	345-01030-0
Nissan	NSD40B, NSD40B2	40	4-Stroke TLDI	2010–2014	345010300M
Nissan	NSD50B, NSD50B2	50	4-Stroke TLDI	2010–2014	345010300M

Technical Specs

Product Type: Thermostat with Gasket and Seals
Installation: Direct OEM replacement
Temperature Rating: 122°F (50°C)
Housing Material: Metal
Housing Color: Silver/Metallic
Operating Temperature: 122°F (50°C) opening temperature

What’s in the Box

1 x Thermostat (346-01030-0/345-01030-0)
1 x Thermostat Housing Gasket
2 x Thermostat Seals

Installation Notes

Ensure the engine is completely cool and disconnect the battery.
Drain the engine coolant to a level below the thermostat housing.
Locate and remove the bolts securing the thermostat housing cover.
Carefully extract the old thermostat, gasket, and seals. Note their orientation.
Thoroughly clean the mating surfaces of the thermostat housing and cover to remove old gasket material or corrosion.
Install the new thermostat, seals, and gasket in the correct position.
Re-secure the housing cover and tighten the bolts to the manufacturer-specified torque.
Refill the cooling system, reconnect the battery, and start the engine, checking carefully for any leaks.

Troubleshooting & FAQ

How do I know if my thermostat is failing?

Common signs of a faulty thermostat include the engine overheating, running too cool (which can cause poor performance and fuel economy), or erratic readings on the temperature gauge. A visual inspection may show it's stuck open or closed.

What is the significance of the 122°F (50°C) temperature rating?

This is the designated temperature at which the thermostat begins to open, allowing coolant to flow from the engine to the radiator. It is critical for maintaining the engine's designed operating temperature for optimal performance and efficiency.

Is this a complete kit for the job?

Yes, this kit includes the thermostat, the primary thermostat housing gasket, and two seals, providing all the essential components for a typical replacement.

Will this fit if my model year isn't listed?

The compatibility table is comprehensive but may not cover every single production year. The most reliable method is to cross-reference the OEM part number from your engine's service manual. If it matches one of the listed replacement numbers, it will fit.

How often should a thermostat be replaced?

Thermostats don't have a fixed service interval, but it's wise to replace them during any major cooling system service or every few hundred hours as preventative maintenance. They should be replaced immediately if they fail.

What's the difference between OEM and this aftermarket part?

This listing is an aftermarket replacement (not OEM). It has been engineered to meet or exceed original equipment manufacturer (OEM) specifications for fit, form, and function, using comparable materials. Our parts are made in an ISO 9002 certified facility and are batch-inspected for quality assurance.

What are the shipping speed and cost?

We ship worldwide quickly—typical transit time is 5–15 days. Standard shipping is free for most orders. Expedited shipping options, if available for your location, will be presented at checkout.

What is the warranty and return policy?

This product is covered by a 1-year warranty against manufacturing defects under normal marine use. Should an issue arise, please contact our support team with your order details. Returns are accepted within our standard window, provided the item is unused and in its original packaging. See our full policy page or contact us for instructions.

Safety & Important Info

Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
This is an aftermarket replacement, not an OEM component.
Professional installation is recommended for safety and performance.

About Sea Sierra

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Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.

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