Sierra 18-3646 Thermostat Kit, 140F, Replaces GM 4765100, Fits 228/305 V-8 1977-1982

The Sierra 18-3646 Thermostat Kit is a complete cooling-system repair kit built around a 140 degree F thermostat for GM 228/305 cubic inch V-8 marine engines produced 1977-1982. Rather than supplying just the thermostat, the kit bundles every gasket needed to reseal the housing during replacement, so the job can be completed in one pass without having to source individual gaskets separately. The thermostat is manufactured to meet or exceed the specifications of the original equipment part it replaces, making it a straightforward drop-in for engines using the housing and drain configuration covered by this part number.

Because marine cooling systems rely on the thermostat opening at the correct temperature to regulate engine operating temperature, using the correct 140 degree F unit for this engine family helps maintain proper heat management and protect against overheating or over-cooling. The kit is intended for engine cooling system service and is a routine maintenance item that should be replaced any time cooling performance is in question or during a scheduled overhaul.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3646
• Product Type: Thermostat Kit
• Thermostat Opening Temperature: 140 degrees F
• Material: Copper
• Weight: 0.15 pounds
• UPC: 808282100919
• Kit Contents: Thermostat (18-3551), Thermostat Cover Gasket (18-2553), Thermostat Cover Gasket (18-2834), Thermostat Gasket (18-2844), Thermostat Gasket (18-2917)
• Fitment: GM 228/305 cubic inch V-8 engines, 1977-1982

Fitment

• GM 228/305 cubic inch V-8 engines, 1977-1982

Replaces (OEM)

• 4765100
• 6218461
• 18-1993
• 18-1977-1
• 18-3551
• 18-2844
• 18-0398

Frequently Asked Questions

What temperature does the Sierra 18-3646 thermostat open at? 140 degrees F is the opening temperature for the thermostat included in the Sierra 18-3646 Thermostat Kit.

What is included in the Sierra 18-3646 Thermostat Kit? The kit contains a 140 degree F thermostat (18-3551) along with four gaskets: two thermostat cover gaskets (18-2553 and 18-2834) and two thermostat gaskets (18-2844 and 18-2917), covering everything needed to reseal the housing during replacement.

Which engines does the 18-3646 thermostat kit fit? This kit is built for GM 228/305 cubic inch V-8 engines from 1977-1982.

What OEM part numbers does the 18-3646 kit replace? The Sierra 18-3646 Thermostat Kit replaces OEM numbers 4765100, 6218461, 18-1993, 18-1977-1, 18-3551, 18-2844, and 18-0398.

Is the Sierra 18-3646 a genuine OEM part or an aftermarket replacement? It is an aftermarket replacement manufactured by Sierra to meet or exceed the specifications of the original equipment thermostat it replaces.

How much does the thermostat kit weigh? The Sierra 18-3646 Thermostat Kit weighs 0.15 pounds.

Do I need to buy separate gaskets when replacing the thermostat? No, the 18-3646 kit already includes the two thermostat cover gaskets and two thermostat gaskets needed to complete the reseal, so no additional gaskets are required.

What material is the thermostat made from? The thermostat in the Sierra 18-3646 kit is made of copper.

Can this kit be cross-referenced by GM part number 4765100? Yes, GM part number 4765100 is one of the OEM numbers that the Sierra 18-3646 Thermostat Kit replaces.

What is the UPC for the Sierra 18-3646 Thermostat Kit? The UPC for this kit is 808282100919.