Sierra 18-3674 Thermostat Kit, Interchangeable with GLM 13280, for Johnson/Evinrude Outboards

The Sierra 18-3674 Thermostat Kit is a complete replacement kit for Johnson/Evinrude outboard cooling systems, bundling the thermostat, valve components, gasket, and hardware needed to restore proper engine temperature regulation in a single package. Marine thermostats and their seals wear out over time from constant exposure to heat cycling and raw water, which can cause an engine to run too hot or too cold, so replacing the full kit at once -- rather than just the thermostat -- ensures the gaskets, valve, and spring are all fresh and sealing correctly together.

This kit includes the 18-3543 thermostat along with a full set of supporting parts: an 18-1219 grommet gasket, an 18-0182 thermostat gasket, an 18-3135 stainless steel bolt, an 18-2546 thermostat gasket, an 18-3567 rubber valve, an 18-3562 valve cup, an 18-1243 valve spring, an 18-3563 poppet relief valve, and an 18-3565 retainer. Sierra designs its cooling system parts to meet or exceed the original equipment they replace, and this kit is built for boat owners performing routine cooling system maintenance or troubleshooting an overheating outboard.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3674
• Product Type: Thermostat Kit
• Weight: 0.1 pounds
• UPC: 808282244019
• Interchangeable With: GLM 13280
• Use With: 18-3543 Thermostat
• Kit Contents: 18-3543 Thermostat, 18-1219 Grommet Gasket, 18-0182 Thermostat Gasket, 18-2546 Thermostat Gasket, 18-3135 Stainless Steel Bolt, 18-3567 Rubber Valve, 18-3562 Valve Cup, 18-1243 Valve Spring, 18-3563 Poppet Relief Valve, 18-3565 Retainer
• Material: Stainless steel and rubber components

Fitment

For the complete thermostat kit including gaskets and spring on Johnson/Evinrude outboards, use Sierra 18-3674.

Replaces (OEM)

• GLM 13280

Frequently Asked Questions

What is included in the Sierra 18-3674 Thermostat Kit? The kit contains the 18-3543 thermostat plus an 18-1219 grommet gasket, 18-0182 thermostat gasket, 18-2546 thermostat gasket, 18-3135 stainless steel bolt, 18-3567 rubber valve, 18-3562 valve cup, 18-1243 valve spring, 18-3563 poppet relief valve, and 18-3565 retainer, giving you every part needed for a complete thermostat replacement.

Is the Sierra 18-3674 a complete thermostat kit or just the thermostat? It is the complete kit, including the gaskets and spring, not just the standalone thermostat. Sierra part 18-3674 is specifically the full kit version for a proper reseal.

Does the Sierra 18-3674 cross-reference to any other part numbers? Yes, the Sierra 18-3674 Thermostat Kit is interchangeable with GLM 13280.

How much does the Sierra 18-3674 Thermostat Kit weigh? The kit weighs 0.1 pounds.

What outboard brand is the Sierra 18-3674 designed for? This kit is built for Johnson/Evinrude outboard cooling systems, supplying the thermostat and related sealing hardware for that application.

What thermostat is used with the Sierra 18-3674 kit? The kit uses and includes the 18-3543 thermostat.

Is Sierra 18-3674 genuine Sierra or aftermarket? It is a genuine Sierra part, manufactured by Sierra International to meet or exceed the specifications of the original equipment it replaces.

What is the UPC for the Sierra 18-3674 Thermostat Kit? The UPC is 808282244019.

Why replace the whole thermostat kit instead of just the thermostat? Replacing the full 18-3674 kit ensures the gaskets, valve, spring, and retainer are all replaced together with the thermostat, so every sealing surface in the cooling circuit is fresh rather than mixing a new thermostat with worn gaskets.

What material are the components in the 18-3674 kit made of? The kit includes stainless steel hardware (the 18-3135 bolt) and rubber sealing parts (the 18-3567 valve), along with the thermostat and gasket components.

Can the Sierra 18-3674 be used for routine maintenance or only for repairs? It works for both: boat owners use the 18-3674 kit for scheduled cooling system maintenance as well as for correcting overheating caused by a failed thermostat or worn gaskets.