Thermostat Kit – Fits Johnson/Evinrude V4 Crossflow 65-140 HP (Replaces 434841, 18-3673)
Thermostat Kit – Fits Johnson/Evinrude V4 Crossflow 65-140 HP (Replaces 434841, 18-3673) is backordered and will ship as soon as it is back in stock.
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Thermostat Kit – Fits Johnson/Evinrude V4 Crossflow 65-140 HP (Repl...
Thermostat Kit – Fits Johnson/Evinrude V4 Crossflow 65-140 HP (Replaces 434841, 18-3673) is backordered and will ship as soon as it is back in stock.
Product Details
This is a complete Thermostat Kit – Fits Johnson/Evinrude V4 Crossflow 65-140 HP engines from approximately 1978 to 1995. It is designed as a direct-fit replacement for the dual thermostat system in various models, including 80 HP Jet, 85–140 HP outboards, ensuring your engine maintains the correct operating temperature for optimal performance and longevity.
This kit serves as a direct interchange for Sierra 18-3673, GLM 13270, and OMC/BRP part numbers 434841, 5005440, 437414, 393659, 377148, 377612, 378065, 321897, 332369, 318395, 321692, and 317245.
- Engineered as a direct OEM replacement for straightforward installation.
- Includes two 143°F (62°C) stainless steel thermostats and all necessary seals and hardware for a complete service.
- Specifically for V4 Crossflow engines; not compatible with 60° V4 models.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Sierra | 18-3673 |
| GLM | 13270 |
| OMC/BRP | 434841 |
| OMC/BRP | 5005440 |
| OMC/BRP | 437414 |
| OMC/BRP | 393659 |
| OMC/BRP | 377148 |
| OMC/BRP | 377612 |
| OMC/BRP | 378065 |
| OMC/BRP | 321897 |
| OMC/BRP | 332369 |
| OMC/BRP | 318395 |
| OMC/BRP | 321692 |
| OMC/BRP | 317245 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Johnson/Evinrude owners, this kit is designed for the V4 Crossflow engine architecture. Please verify your model is not a 60° V-engine, as they use a different cooling system.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Johnson/Evinrude | V4 Crossflow | 65 | 2-Stroke | 434841 | Not explicitly mentioned in all sources | |
| Johnson/Evinrude | V4 Crossflow | 80 Jet | 2-Stroke | 1994–1995 | 434841 | |
| Johnson/Evinrude | V4 Crossflow | 85 | 2-Stroke | 1978–1980, 1993–1995 | 434841 | |
| Johnson/Evinrude | V4 Crossflow | 88 | 2-Stroke | 1987–1995 | 434841 | |
| Johnson/Evinrude | V4 Crossflow | 90 | 2-Stroke | 1981–1995 | 434841 | Includes 1994 Jet model |
| Johnson/Evinrude | V4 Crossflow | 100 | 2-Stroke | 1979–1980, 1990–1995 | 434841 | Includes Commercial 1984–1995 |
| Johnson/Evinrude | V4 Crossflow | 110 | 2-Stroke | 1985–1989 | 434841 | |
| Johnson/Evinrude | V4 Crossflow | 112 | 2-Stroke | 1994–1995 | 434841 | |
| Johnson/Evinrude | V4 Crossflow | 115 | 2-Stroke | 1977–1995 | 434841 | Model 115790S only for 1977; All Crossflow models 1978–1995 |
| Johnson/Evinrude | V4 Crossflow | 140 | 2-Stroke | 1978–1985 | 434841 |
Technical Specs
- Product Type
- Marine Outboard Thermostat Kit
- Installation
- Direct OEM replacement
- Thermostat Temperature
- 143°F (62°C)
- Engine Type
- V4 Crossflow
- Housing Material
- Stainless Steel (thermostat)
- Operating Temperature
- 143°F (62°C) opening temperature
- Warranty
- 1 Year (YiheoZux brand)
- Other Technical Attributes
- For dual thermostat system
What’s in the Box
- 2 x Stainless thermostats (143°F)
- 2 x Thermostat base seals
- 2 x Poppet valves
- 2 x Poppet seat seals
- 2 x Poppet springs
- 2 x Gaskets
Installation Notes
- Disconnect the battery and ensure the engine is cool to the touch.
- Locate the thermostat housings on the cylinder heads. It may be necessary to remove the engine cover or other components for access.
- Carefully remove the bolts securing the thermostat covers. Note the orientation of all parts.
- Remove the old thermostats, gaskets, seals, and poppet valve assemblies.
- Clean all mating surfaces thoroughly, ensuring they are free of old gasket material and corrosion.
- Install the new poppet valves, springs, and seals into the thermostat housings.
- Place the new gaskets and thermostats in their correct positions. Ensure the thermostats are oriented correctly.
- Reinstall the thermostat covers and tighten the bolts to the manufacturer's specified torque in a crisscross pattern.
- Reconnect the battery and start the engine, checking for leaks around the housings.
- Allow the engine to reach operating temperature to verify the new thermostats open correctly.
Troubleshooting & FAQ
How do I know if this kit fits my V4 engine?
This kit is specifically for Johnson/Evinrude V4 Crossflow engines made between 1978 and 1995. It will NOT fit the 60° "Looper" V4 models. Please check your engine's service manual or model number to confirm it is a Crossflow design before purchasing. The compatibility table provides a detailed list of known HP ratings and years.
What are the signs of a failing thermostat?
Common symptoms include engine overheating at idle or low speeds, or the engine failing to reach its normal operating temperature (running too cold). An engine that runs too cold can suffer from poor fuel efficiency, carbon buildup, and increased wear. Overheating can cause severe internal damage.
Why does this kit include two thermostats?
The Johnson/Evinrude V4 Crossflow engines use a dual thermostat system, with one thermostat for each cylinder bank. It is critical to replace both at the same time to ensure balanced engine cooling and performance.
Is the 143°F temperature correct for my engine?
Yes, 143°F (62°C) is the standard OEM temperature rating for these V4 Crossflow models. Using the correct temperature thermostat is essential for proper engine combustion, performance, and longevity.
Can I replace just the thermostats and reuse the old gaskets?
We strongly advise against reusing old gaskets, seals, or springs. This kit provides all the necessary components for a complete and reliable service. Reusing old parts can lead to leaks and improper seating, causing the engine to overheat.
What's the difference between OEM and this aftermarket kit?
This listing is an aftermarket replacement (not OEM). It's built to OEM-level specifications with comparable materials. Our parts are manufactured in an ISO 9002 facility and are batch-inspected for quality and consistency, offering a reliable alternative at a better value.
How fast is shipping and what does it cost?
We ship worldwide quickly—typical transit is 5–15 days. Standard shipping is free for most orders, with expedited options available at checkout depending on your location.
What is the warranty and return policy?
This product is covered by a 1-year warranty against manufacturing defects under normal use. If you encounter any issues, 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 condition. See our policy page or reach out 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
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- 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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