Thermostat & Gasket Kit – Fits MerCruiser 120/140/165 GM Engines and Chrysler Force 55/60/65 HP Engines, 140°F
Thermostat & Gasket Kit – Fits MerCruiser 120/140/165 GM Engines and Chrysler Force 55/60/65 HP Engines, 140°F is backordered and will ship as soon as it is back in stock.
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Thermostat & Gasket Kit – Fits MerCruiser 120/140/165 GM Engine...
Thermostat & Gasket Kit – Fits MerCruiser 120/140/165 GM Engines and Chrysler Force 55/60/65 HP Engines, 140°F is backordered and will ship as soon as it is back in stock.
Product Details
This 140°F (60°C) thermostat and gasket kit is a replacement cooling-system service kit for selected MerCruiser GM stern-drive engines and Chrysler Force outboard engines. It is listed for MerCruiser 120 and 140 GM applications, including 2.5L and 3.0L GM engines, the 3.0L LX, and 165 GM applications. It is also listed for Chrysler Force 55, 60, and 65 HP engines.
The kit combines a thermostat and the matching thermostat housing gasket for a convenient replacement during cooling-system service. Always compare the thermostat, gasket, housing, engine model, and manufacturer part number with the parts being replaced before installation.
- 140°F (60°C) thermostat rating.
- Kit includes one thermostat and one thermostat gasket.
- Reference kit number: Sierra 18-3650.
- Designed for the listed MerCruiser GM and Chrysler Force applications.
Part Number Matrix
The following manufacturer and aftermarket references are associated with this thermostat kit or its included components. Reference numbers do not replace confirmation of the engine model and application.
| Application or Component | Reference Number |
|---|---|
| MerCruiser thermostat kit | 18-3650 |
| MerCruiser thermostat | 59078, 59078A1, 59078T3/Q3, 59078B |
| Included thermostat | 18-3550 |
| Included thermostat gasket | 18-2831 |
| Thermostat gasket reference | 27-47590-1 |
| Chrysler Force applications | F85068-2, F84068-2, F85068-1, F85068 |
Engine & Model Compatibility
Confirm the manufacturer, engine rating, displacement, and original part reference before ordering. The available application information does not specify a universal year or serial-number range for every listed engine.
| Brand | Engine or Model | Rated HP | Displacement or Description | Associated References |
|---|---|---|---|---|
| MerCruiser | 120 GM | 120 HP | GM application; 2.5L GM | 59078, 59078A1, 59078T3/Q3, 59078B |
| MerCruiser | 140 GM | 140 HP | 3.0L GM | 59078, 59078A1, 59078T3/Q3, 59078B |
| MerCruiser | 3.0L LX GM | Not separately stated | 3.0L LX GM | 59078, 59078A1, 59078T3/Q3, 59078B |
| MerCruiser | 165 GM | 165 HP | GM application | 59078, 59078A1, 59078T3/Q3, 59078B |
| Chrysler Force | Force outboard | 55, 60, or 65 HP | Application-specific fitment | F85068-2, F84068-2, F85068-1, F85068 |
Technical Specifications
- Product Type
- Thermostat and gasket kit
- Thermostat Rating
- 140°F (60°C)
- Included Kit Reference
- 18-3650
- Included Thermostat Reference
- 18-3550
- Included Gasket Reference
- 18-2831; gasket reference 27-47590-1
- Installation
- Replacement service installation; confirm application and housing configuration before fitting
What’s in the Box
- 1 x 140°F (60°C) thermostat
- 1 x thermostat housing gasket
Installation Notes
- Make sure the engine is completely cool before beginning work. Follow the manufacturer’s service procedures and disconnect the battery where applicable.
- Drain or collect coolant as required for the engine configuration and locate the thermostat housing.
- Place a suitable cloth or container beneath the housing to catch residual coolant, then remove the housing-cover fasteners.
- Remove the old thermostat and gasket, noting the thermostat orientation before removal.
- Clean the housing and cover mating surfaces carefully. Remove old gasket material without damaging the sealing surfaces.
- Install the new thermostat in the same orientation as the original part and position the new gasket correctly.
- Reinstall the housing cover and tighten the fasteners to the engine manufacturer’s specified torque.
- Restore the cooling system using the correct coolant or water configuration for the engine, then check the fluid level.
- Run the engine according to the service manual and inspect the housing for leaks while monitoring operating temperature.
Troubleshooting & FAQ
What does this kit include?
It includes one 140°F (60°C) thermostat and one thermostat housing gasket. The kit reference is 18-3650; the included component references are 18-3550 and 18-2831.
Which engines are listed for this kit?
The company application data lists MerCruiser 120 GM, 2.5L GM, 140 GM, 3.0L GM, 3.0L LX GM, and 165 GM applications, plus Chrysler Force 55, 60, and 65 HP applications. Confirm the exact engine and original part number before purchase.
Is 140°F the correct temperature rating?
This kit is specified as a 140°F (60°C) thermostat. Use the temperature rating specified for your particular engine and verify it against the service manual before installation.
My model or serial number is not listed. Will it fit?
Fitment should not be determined from horsepower alone. Compare the engine brand, model, displacement, original thermostat, gasket, and applicable reference number with the information above or with the manufacturer’s service documentation.
Can I reuse the old gasket?
No. A new gasket is included to provide a fresh seal during thermostat replacement. Reusing a compressed or damaged gasket can lead to leaks.
Why is the engine still overheating after replacement?
Continued overheating can result from other cooling-system problems, including restricted passages, insufficient coolant flow, a damaged water pump or impeller where applicable, air in the system, or a faulty temperature-sensing component. Follow the engine manufacturer’s diagnostic procedures.
Is this an OEM component?
This listing is for a replacement thermostat and gasket kit. The listed manufacturer and aftermarket reference numbers are provided for application identification; verify the exact brand and construction shown for the item supplied.
Shipping speed and cost
Available shipping methods, delivery estimates, and costs are shown at checkout and may vary by destination.
Warranty and returns
Warranty and return eligibility are subject to the seller’s current policy. Contact support with your order details if you need assistance.
Safety & Important Information
- Verify the engine model, displacement, horsepower, original part references, and thermostat orientation before ordering or installing.
- Do not rely on a shared part number alone when engine model, year, serial range, or housing configuration differs.
- Work only on a fully cooled engine and follow the applicable manufacturer service instructions.
- Professional installation is recommended if you are not familiar with marine engine cooling systems.
About Sea Sierra
- Marine Replacement Parts — We supply replacement components for common marine engine service applications.
- Application-Focused Information — Reference numbers and fitment details are provided to help customers compare their original parts.
- Support When You Need It — Contact our team with your engine model and original part details when application guidance is needed.
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