Thermostat Kit – Fits OMC Cobra & Volvo Penta 4.3L-5.8L V6/V8 (Replaces 383307, 18-3653, 3856961)

Thermostat Kit – Fits OMC Cobra & Volvo Penta 4.3L-5.8L V6/V8

This 160°F thermostat kit is designed for a wide range of OMC Cobra and Volvo Penta sterndrive applications. It fits various V6 and V8 engines from 3.8L to 7.5L, covering models manufactured from the 1970s through the 1990s. Compatible Volvo Penta applications include 4.3GL, 4.3GS, 4.3Gi, 5.0FL, 5.0Fi, 5.7GL, 5.7Gi, 5.8FL, 5.8Fi, and 5.8FSi engines.

This kit serves as a direct replacement for multiple OEM and aftermarket part numbers, including OMC 379754, 383307, 3856961; Sierra 18-3653, 18-3554; GLM 13430, 13060; and Mallory 9-43156, 9-43021.

• Operating Temperature: Opens at a reliable 160°F (71°C) to maintain optimal engine temperature.
• Complete Kit: Includes the thermostat, gaskets, and O-ring needed for a full replacement.
• Installation Method: Designed as a direct-fit replacement for the original thermostat assembly.

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.

OMC Cobra Applications

Volvo Penta Applications

Technical Specifications

Package Contents

• 1 x 160°F Thermostat (Replaces OMC 3856961)
• 1 x Thermostat Housing Gasket (Replaces OMC 3852111)
• 1 x O-ring (Replaces OMC 3852071)
• 1 x Gasket (Replaces OMC 314809)
• 1 x Gasket (Replaces OMC 313416)

Installation Guide

1. Ensure the engine is completely cool. Disconnect the battery for safety.
2. Place a catch pan under the thermostat housing and drain the coolant from the engine block.
3. Locate the thermostat housing on the engine and loosen the hose clamps on any connected hoses.
4. Remove the bolts securing the housing cover. You may need to gently tap it to break the seal.
5. Take note of the old thermostat's orientation before removing it.
6. Remove the old thermostat and the old gasket or O-ring.
7. Thoroughly clean both the housing and the engine block mating surfaces to remove any old gasket material or sealant.
8. Install the new thermostat in the correct orientation, followed by the new gasket and/or O-ring.
9. Re-secure the housing cover and tighten the bolts to the manufacturer's specified torque.
10. Reconnect the hoses and tighten the clamps.
11. Refill the cooling system with the appropriate coolant.
12. Start the engine, check for any leaks, and monitor the temperature gauge to ensure it reaches and maintains the correct operating temperature.

Troubleshooting & FAQ

Q: What are the signs of a failing thermostat?

A: Common signs of a faulty thermostat include engine overheating, the temperature gauge reading erratically or showing unusually high or low temperatures, and poor engine performance. If the thermostat is stuck open, the engine may not reach its proper operating temperature.

Q: How can I confirm this thermostat kit will fit my specific engine?

A: To ensure compatibility, please check your original part number against our "Part Number Cross-Reference" list. Additionally, verify your engine's model and year in the "Compatible Engine Models" tables provided on this page.

Q: How often should a marine engine thermostat be replaced?

A: For preventative maintenance, it is recommended to inspect your thermostat annually and consider replacement every 3-5 years, depending on usage. Engines operated in saltwater may require more frequent inspections and replacements due to accelerated corrosion.

Q: Is this an OEM 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.