Thermostat Cover Gasket – Fits Johnson/Evinrude Outboards (Replaces 329830/0329830/777385/0777385)
Thermostat Cover Gasket – Fits Johnson/Evinrude Outboards (Replaces 329830/0329830/777385/0777385) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Thermostat Cover Gasket – Fits Johnson/Evinrude Outboards (Replaces...
Product Details
This aftermarket Thermostat Cover Gasket is designed for a precise fit on various Johnson/Evinrude 2-stroke outboard engines, including multiple 50 HP and 70 HP models manufactured between 1986 and 2004. It creates a reliable, watertight seal between the thermostat cover and the engine block, preventing coolant leaks and ensuring proper engine temperature regulation.
This gasket is a direct replacement for Johnson/Evinrude OEM part numbers 329830, 0329830, 777385, and 0777385, as well as Sierra cross-reference 18-1202.
- Installs as a direct replacement for the original part.
- Engineered for use in marine environments with 2-stroke gasoline engines.
- Creates a durable, watertight seal to protect engine integrity.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Johnson/Evinrude | 329830 |
| Johnson/Evinrude | 0329830 |
| Johnson/Evinrude | 777385 |
| Johnson/Evinrude | 0777385 |
| Sierra | 18-1202 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
This component is designed to fit a range of Johnson/Evinrude outboard engines. Please verify your specific model and year against the details provided.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| Johnson/Evinrude | Various | 50 | 2-Stroke | 1995–2004 | 329830/0329830 | |
| Johnson/Evinrude | Various | 70 | 2-Stroke | 1986–2001 | 329830/0329830 | |
| Johnson/Evinrude | Various | Various | 2-Stroke | 777385/0777385 | Alternate OEM number |
Technical Specs
- Product Type
- Thermostat Cover Gasket
- Installation
- Direct replacement
- Fuel Type
- Gas (for 2-stroke engines)
- Housing Material
- OEM-style gasket material
- Dimensions
- 4.0″ x 5.13″ x 1.06″
- Operating Temperature
- Compatible with marine cooling system operating temperatures
- Other Technical Attributes
- Designed to create a watertight seal between the thermostat cover and engine
What’s in the Box
- 1 x Thermostat Cover Gasket (Replaces 329830/0329830/777385/0777385)
Installation Notes
- Ensure the engine is completely cool and disconnect the battery for safety.
- Locate the thermostat housing on the engine. You may need to remove an engine cover or other components to access it.
- Carefully remove the bolts holding the thermostat cover in place. Note their length and position if they differ.
- Gently pry the cover loose. Remove the old gasket and thermostat, noting their orientation.
- Thoroughly clean both the engine block and thermostat cover mating surfaces. All traces of old gasket material must be removed to ensure a proper seal.
- Place the new thermostat into the housing, followed by the new gasket.
- Re-install the cover and tighten the bolts in a crossing pattern to the manufacturer-specified torque to ensure even pressure.
- Reconnect the battery, start the engine, and carefully check for any coolant leaks around the housing as the engine warms up.
Troubleshooting & FAQ
How do I know if this gasket will fit my specific model?
This gasket is designed for various 50–70 HP Johnson/Evinrude 2-stroke outboards (1986–2004). The most reliable method is to cross-reference your engine's original part number with those listed in our Part Number Matrix. If you're unsure, consulting your engine's service manual is always recommended.
What are the signs of a failing thermostat cover gasket?
The most common symptoms of a bad gasket are visible coolant leaks or dried coolant residue around the thermostat housing. This can lead to engine overheating, poor performance, or even white steam emanating from the engine cowling.
How often should this gasket be replaced?
It's best practice to replace the thermostat gasket anytime the thermostat itself is replaced for maintenance. You should also replace it immediately if you notice any signs of a leak or damage during routine engine inspection.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
Payment & Security
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