Thermostat Kit – Fits Volvo Penta/OMC 4.3L/5.0L/5.7L/5.8L V6/V8 (Replaces 3856961, 18-3677)

Thermostat Kit – Fits Volvo Penta/OMC 4.3L/5.0L/5.7L/5.8L V6/V8 (Replaces 3856961, 18-3677)

This thermostat kit is designed for Volvo Penta and OMC Cobra 4.3L–5.8L engines (1993–2003), including both V6 (4.3L) and V8 (5.0L, 5.7L, 5.8L) applications in various sterndrive configurations.

This is a direct aftermarket replacement for Volvo Penta part numbers 3856961 and 383307, as well as OMC/Sierra part numbers 18-3677 and 47-3677.

• Engineered for direct-fit installation.
• Maintains proper engine operating temperature at 160°F (71°C).
• Complete kit includes the thermostat, gasket, and O-ring for a full replacement.

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below.

Technical Specifications

Package Contents

• 1 x Thermostat (Part #3856961)
• 1 x Gasket (Part #3852111)
• 1 x O-Ring (Part #3852071)

Installation Guide

1. Ensure the engine is completely cool and disconnect the negative battery terminal for safety.
2. Drain the engine coolant to a level below the thermostat housing.
3. Locate and carefully remove the bolts securing the thermostat housing.
4. Lift the housing away and remove the old thermostat and gasket.
5. Thoroughly clean the mating surfaces of the housing and the engine block.
6. Install the new gasket and O-ring into the housing.
7. Insert the new thermostat, ensuring it is correctly oriented as per your service manual.
8. Re-secure the housing and tighten the bolts to the manufacturer's recommended torque.
9. Refill the cooling system with the appropriate coolant.
10. Reconnect the battery, start the engine, and check for any leaks and proper temperature gauge operation.

Troubleshooting & FAQ

Q: How do I confirm this kit fits my engine?
A: Please review the "Compatible Engine Models" and "Part Number Cross-Reference" tables. It is critical to verify that your specific engine model, year, and original part number are listed to ensure correct fitment.

Q: What are common signs of a bad thermostat?
A: Symptoms of a failing thermostat include engine overheating, the engine not reaching normal operating temperature, erratic temperature readings on the gauge, and potential coolant leaks around the housing.

Q: How often should a marine thermostat be replaced?
A: We recommend inspecting the thermostat annually as part of your regular cooling system maintenance. Consider replacing it every 2-3 years as a preventative measure to avoid engine damage, especially in saltwater environments.

Q: Is this an OEM part or an aftermarket part?
A: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

Q: How fast do you ship and how much does it cost?
A: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

Q: What is your warranty and return policy?
A: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.