Sierra Thermostat Kit 18-3651, 142 Degree, for GM 327/350 V-8 and Ford Stern Drive Engines

The Sierra 18-3651 Thermostat Kit is a marine engine cooling thermostat built to regulate coolant flow and keep stern drive engines operating at a stable temperature. It carries a 142 degree Fahrenheit opening rating, matching the factory-specified temperature for a range of GM and Ford based stern drive powerheads. Marine thermostats like this one are a wear item that should be checked and replaced as part of routine cooling system maintenance, since a stuck-open or stuck-closed thermostat can cause overheating or poor engine warm-up.

Sierra manufactures this kit to meet or exceed the performance of the original equipment part it replaces, and it is built for the demands of continuous marine duty in a harsh operating environment. The 18-3651 is used across a number of GM 327 and 350 cubic inch V-8 applications as well as Ford-based stern drive engines, so confirming your engine model and part number before ordering is important to ensure proper fit.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3651
• Temperature Rating: 142 degrees Fahrenheit
• Weight: 0.19 pounds
• UPC: 030999316158
• GTIN: 00030999316158
• Fitment: GM 327 and 350 cubic inch V-8, Ford, and MCM/MIE stern drive engines

Fitment

• GM 225 hp, 327 cubic inch V-8, 1967-1969
• MCM/MIE 250 hp, 327 cubic inch V-8, 1968-1969
• 250 hp, 350 cubic inch V-8, 1977
• Ford 225/225S stern drive engines
• Ford 255 hp stern drive engines
• 260 hp, 350 cubic inch V-8, 1978-1982

Replaces (OEM)

• GLM 13380
• Mallory 9-43152

Frequently Asked Questions

What temperature does the Sierra 18-3651 thermostat open at? The Sierra 18-3651 thermostat kit is rated to open at 142 degrees Fahrenheit, which matches the factory temperature specification for the GM and Ford stern drive engines it fits.

Does the 18-3651 fit a GM 350 V-8 stern drive engine? Yes, the Sierra 18-3651 is used on GM 350 cubic inch V-8 stern drive applications, including 250 hp and 260 hp configurations, in addition to GM 327 cubic inch V-8 engines.

Will the 18-3651 work on a Ford-powered stern drive? Yes, this thermostat kit also fits Ford-based stern drive engines, including 225/225S and 255 hp applications, so it covers both GM and Ford powerheads depending on the engine's part number requirements.

What does the 18-3651 kit include? The Sierra 18-3651 is sold as a thermostat kit, meaning it includes the 142 degree thermostat itself as the core component for the cooling system service.

Is the Sierra 18-3651 an OEM part or aftermarket? The 18-3651 is a Sierra-manufactured aftermarket thermostat kit engineered to meet or exceed the performance of the original equipment thermostat it replaces.

What OEM or other aftermarket thermostats does the 18-3651 replace? This Sierra thermostat kit interchanges with GLM 13380 and Mallory 9-43152, so any of those part numbers point to the same 142 degree thermostat application.

How much does the Sierra 18-3651 thermostat kit weigh? The 18-3651 thermostat kit weighs 0.19 pounds.

How do I know if I need to replace my stern drive thermostat? A marine thermostat like the Sierra 18-3651 should be replaced if the engine is overheating, running too cool, or has an inconsistent operating temperature, since a stuck thermostat is a common cause of these symptoms.

Can I use the 18-3651 on a 1968 GM 327 V-8 stern drive engine? Yes, the Sierra 18-3651 is listed for GM 250 hp, 327 cubic inch V-8 applications built in 1968-1969, among other GM and Ford engine years.

Is the 18-3651 brand new or remanufactured? The Sierra 18-3651 is a new thermostat kit, not a remanufactured or used part.