Sierra 18-3673 Thermostat Kit for V-4 Crossflow Outboard Engines

The Sierra 18-3673 Thermostat Kit is a complete replacement kit for the cooling system on V-4 Crossflow outboard engines. Rather than buying individual worn components separately, this kit bundles every part needed to service the thermostat housing in a single package, saving time on the workbench and ensuring the gaskets, grommet, relief valve, and springs are all matched and fresh at the same time.

At the core of the kit is the 18-3543 thermostat, paired with two thermostat gaskets (18-0675 and 18-0977) that seal the housing on both sides. An 18-2391 grommet seats the poppet valve assembly, while the 18-3564 poppet relief valve and 18-1243 valve springs regulate water flow and pressure relief during operation. The hardware components in the kit are iron construction for durability in a marine cooling environment.

This kit is built for V-4 Crossflow outboard engines. Sierra also offers the 18-3674 Thermostat Kit as the equivalent version for V-6 Crossflow engines, so buyers should confirm engine configuration before ordering to make sure the 18-3673 is the correct kit.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3673
• Product Type: Thermostat Kit
• Engine Application: V-4 Crossflow
• Kit Contents: Thermostat, 2 thermostat gaskets, grommet, poppet relief valve, valve springs
• Included Thermostat Part Number: 18-3543
• Material: Iron
• Weight: 0.22 pounds
• UPC: 808282258849
• Interchange Number: GLM 13270

Fitment

• V-4 Crossflow outboard engines

Replaces (OEM)

• GLM 13270

Frequently Asked Questions

What is included in the Sierra 18-3673 Thermostat Kit? The kit includes an 18-3543 thermostat, two thermostat gaskets (18-0675 and 18-0977), an 18-2391 grommet, an 18-3564 poppet relief valve, and 18-1243 valve springs.

Which engines does the 18-3673 thermostat kit fit? The Sierra 18-3673 Thermostat Kit is built for V-4 Crossflow outboard engines.

Is the 18-3673 kit interchangeable with any OEM number? Yes, the Sierra 18-3673 Thermostat Kit is interchangeable with GLM 13270.

What material are the components in this thermostat kit made of? The hardware components in the Sierra 18-3673 Thermostat Kit are iron construction.

How much does the Sierra 18-3673 Thermostat Kit weigh? The Sierra 18-3673 Thermostat Kit weighs 0.22 pounds.

Does the 18-3673 kit include gaskets? Yes, two thermostat gaskets are included, part numbers 18-0675 and 18-0977, along with the rest of the 18-3673 kit components.

What thermostat comes with the Sierra 18-3673 kit? The Sierra 18-3673 Thermostat Kit uses the 18-3543 thermostat.

What is the difference between the 18-3673 and 18-3674 thermostat kits? The 18-3673 kit is for V-4 Crossflow engines, while the 18-3674 Thermostat Kit is the equivalent kit for V-6 Crossflow engines; both use the same 18-3543 thermostat but are separate part numbers for their respective engine applications.

Does the 18-3673 kit include a poppet relief valve and springs? Yes, the kit includes an 18-3564 poppet relief valve and 18-1243 valve springs along with the thermostat, gaskets, and grommet.

Is the Sierra 18-3673 a complete thermostat housing rebuild kit? Yes, the Sierra 18-3673 Thermostat Kit bundles the thermostat, both gaskets, grommet, poppet relief valve, and valve springs needed to service the thermostat housing on a V-4 Crossflow outboard in one kit.