Sierra 18-3673 - Johnson/Evinrude V4 Crossflow Thermostat Kit 143°F

Sierra 18-3673 - Johnson/Evinrude V4 Crossflow Thermostat Kit, 143°F

Sierra 18-3673 brings thermostat and associated sealing and relief-valve service components together for compatible Johnson and Evinrude V4 Crossflow outboards. The Sierra catalog identifies the 143°F 18-3543 thermostat for this kit. Choosing by the engine’s Crossflow configuration and model-specific parts diagram helps distinguish this service package from kits for other Johnson/Evinrude cooling systems.

Part Specifications

• Part Number: 18-3673
• Component: Thermostat service kit
• Engine Family: Compatible Johnson/Evinrude V4 Crossflow outboards
• Thermostat Rating: 143°F
• Service Thermostat: 18-3543
• Published Component References: 18-0977 thermostat cover gasket; 18-0675 thermostat gasket; 18-2391 grommet; 18-3564 poppet relief valve; 18-1243 valve spring; 18-3543 thermostat
• Contents Qualification: Component references are seller-listed; individual quantities are not specified here
• Fitment Limitation: Not a universal Johnson/Evinrude V4 or V6 kit; published 90/115 HP application listings exclude 60-degree models
• Packaging Reference: Sierra catalog identifies 18-3673D as display-packaged and 18-3673 as non-display-packaged, not a documented supersession
• Aftermarket Cross-Reference: GLM 13270

Confirm Fitment Before Ordering

Use the parts diagrams available on our website to identify the thermostat service parts for your engine. Alternatively, send us your engine model and serial number by email, text or live chat, and we’ll confirm fitment before ordering. Include the horsepower and model year where known so the V4 Crossflow configuration and any 60-degree-model exclusions can be checked.

Additional Information

• Vendor: Sierra
• Part Number: 18-3673
• Aftermarket Cross-Reference: GLM 13270
• Kit Contents: Seller-listed thermostat, thermostat cover gasket, thermostat gasket, grommet, poppet relief valve and valve spring components; verify individual quantities against the supplied package

The separately listed Sierra 18-3543 143°F thermostat is the service thermostat identified for this kit. A thermostat-only purchase does not provide the kit’s associated gaskets, springs, grommets and relief-valve components.

Installation Notes

Refer to the applicable Johnson/Evinrude service manual for thermostat and relief-valve service, gasket and grommet placement, fastener specifications and cooling-system checks.

Frequently Asked Questions

Q: What temperature thermostat does this kit use?
A: The Sierra catalog identifies thermostat 18-3543, rated at 143°F, for the 18-3673 V4 Crossflow kit.

Q: Does it fit every Johnson or Evinrude V4?
A: No. This is a V4 Crossflow kit, and published 90/115 HP application listings specifically exclude 60-degree models. Verify the complete engine model and serial number.

Q: What service components are listed?
A: Published seller contents identify the thermostat, thermostat cover gasket, thermostat gasket, grommet, poppet relief valve and valve spring. Individual quantities should be checked against the package and engine diagram.

Q: Did 18-3673 replace 18-3673D?
A: The Sierra catalog describes the D suffix as display packaging and the regular number as non-display packaging; that distinction does not establish a supersession.

Q: Is the separately sold 18-3543 thermostat the same as buying the kit?
A: No. It is the thermostat identified for the kit, but purchasing that component alone does not supply the associated service components listed with 18-3673.