Thermostat Kit 378065 18-3673 for Johnson Evinrude 65 80 85 90 100 115 HP V4
Thermostat Kit 378065 18-3673 for Johnson Evinrude 65 80 85 90 100 115 HP V4
Product Overview
Thermostat kit for Johnson and Evinrude V4 outboards from 65 HP to 115 HP, supplied as 1 x thermostat with valve springs, poppet relief valve, grommets and thermostat and cover gaskets. It replaces Johnson Evinrude 378065, 393659, 434841, 437414, 5005440 and 508626, plus Sierra 18-3673. A failed thermostat shows up as an engine that runs cold and sooty, or one that overheats within minutes of starting.
Specifications & Attributes
| Specification | Detail |
|---|---|
| Condition | New / New with tags |
| Type | Thermostat Kit |
| Engine Type | Johnson / Evinrude V4 outboard |
| Horsepower Range | 65 HP - 115 HP |
| Kit Type | Thermostat with springs, poppet valve and gaskets |
| Warranty | Standard |
OEM Cross Reference
| Brand | OEM Part Numbers |
|---|---|
| Johnson / Evinrude | 378065, 393659, 434841, 437414, 5005440, 508626 |
| Sierra | 18-3673 |
| Sierra (thermostat) | 18-3543 |
Compatible Engines
Fits the following Johnson and Evinrude V4 outboards:
| Brand | HP |
|---|---|
| Johnson / Evinrude | 65 HP |
| Johnson / Evinrude | 80 HP |
| Johnson / Evinrude | 85 HP |
| Johnson / Evinrude | 88 HP |
| Johnson / Evinrude | 90 HP |
| Johnson / Evinrude | 100 HP |
| Johnson / Evinrude | 110 HP |
| Johnson / Evinrude | 112 HP |
| Johnson / Evinrude | 115 HP |
What's Included
| Component | Qty |
|---|---|
| Thermostat | 1 |
| Valve Spring (V4 / V6 crossflow) | 2 |
| Poppet Relief Valve (V4 crossflow) | 1 |
| Grommet (V4 crossflow) | 2 |
| Thermostat Gasket | 2 |
| Thermostat Cover Gasket | 2 |
Condition & Warranty
| Item | Detail |
|---|---|
| Condition | New / New with tags |
| Warranty | Standard |
| Packaging | Sealed retail packaging |
Before You Buy
- Verify your engine model, year and serial number before ordering
- Fits Johnson and Evinrude 65-115 HP V4 outboards
- Check the thermostat housing and poppet valve seat for corrosion
- Renew both gaskets with the thermostat — reused ones usually weep
- 30-Day Easy Returns
- Free Worldwide Shipping
- OEM Quality Without the Markup
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Boat Owners' Review
Before You Buy
Frequently Asked Questions
What is your refund policy?
We offer a 14-day hassle-free return on all products. Items must be unused and in original packaging. Every XRmarine part is also covered by our 1-year warranty against manufacturing defects. If something is not right, email us at info@xrmarineparts.com — replacement or full refund, your choice.
See our full Refund Policy for complete details.
How does shipping work?
Free international shipping on every order — no minimums. We operate a global warehouse network with a main distribution centre in Asia (10-20 business days). We also hold stock in regional warehouses across the United States, Germany, the United Kingdom, Australia, and Poland (opening soon) — most orders arrive in 1-3 business days within those countries and in 2-8 business days to nearby regions. Tracking included.
See our full Shipping Policy.
How do you keep prices fair?
We cut out the middlemen. XRmarine sources directly from quality manufacturers and sells at honest prices. Same OEM-quality parts, no dealership markup. Every order comes with free shipping, real expert support, and a 1-year warranty.
Learn more on our About Us page.
What payment methods do you accept?
We currently accept PayPal — a fast, secure way to pay online. Credit card payments (Visa, Mastercard, American Express) and Shopify Payments are being set up and will be available soon. We appreciate your patience.