Thermostat Kit (160°F/71°C) – Fits OMC Cobra & Volvo Penta 3.8-7.5L V6/V8 (Replaces 383307, 18-3653)

Thermostat Kit (160°F/71°C) – Fits OMC Cobra & Volvo Penta 3.8-7.5L V6/V8

This thermostat kit is designed for a wide range of OMC Cobra and Volvo Penta sterndrive engines. It fits V6 and V8 models from 3.8L to 7.5L (90-454HP) manufactured from 1968 and up, ensuring proper engine operating temperature for optimal performance and efficiency.

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

• Operating Temperature: Maintains a consistent engine temperature of 160°F (71°C).
• Complete Kit: Includes the thermostat, O-ring, and necessary gaskets for a full replacement.
• Installation Type: Engineered for direct OEM replacement with no modifications required.

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

Volvo Penta

Technical Specifications

Package Contents

• 1 x Thermostat (Replaces 383307/3856961)
• 1 x O-ring (3852071)
• 1 x Gasket (314809)
• 1 x Gasket (313416)
• 1 x Housing Gasket (3852111)
• 1 x Installation Instructions

Installation Guide

1. Drain Coolant: Ensure the engine is cool. Drain the engine block and manifolds a sufficient amount to bring the coolant level below the thermostat housing.
2. Locate Housing: Find the thermostat housing, typically where the main coolant hose from the circulation pump connects to the top of the engine.
3. Remove Housing: Loosen and remove the bolts securing the housing. Carefully separate the housing from the engine block or manifold.
4. Remove Old Parts: Take out the old thermostat and peel off the old gasket or O-ring. Note the thermostat's orientation before removal.
5. Clean Surfaces: Thoroughly clean the mating surfaces of both the housing and the engine block to remove any old gasket material or corrosion.
6. Install New Thermostat: Place the new thermostat into the recessed groove, ensuring it is oriented correctly. Install the new gasket or O-ring as required.
7. Reassemble: Re-position the housing and tighten the bolts to the manufacturer's recommended torque specifications. Do not overtighten.
8. Refill and Check: Refill the cooling system. Start the engine and let it warm up, checking carefully for any leaks around the housing. Top off coolant as needed.

Troubleshooting & FAQ

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

A: The best way to ensure fitment is to check your engine's model, year, and OEM part number against the compatibility tables provided on this page. Cross-reference your existing thermostat's part number with the numbers listed, such as OMC 383307 or Volvo Penta 3856961.

Q: What are common signs that my thermostat is failing?

A: Common symptoms include engine overheating (running hot) or engine failing to reach operating temperature (running cold). You may also notice erratic temperature gauge readings or coolant leaks around the thermostat housing.

Q: How often should I replace my boat's thermostat?

A: Thermostats are a critical maintenance item. It is recommended to inspect them annually and replace them every 2-3 years, or as part of your routine cooling system service, to prevent overheating and ensure engine longevity.

Q: Is this a 140°F or 160°F thermostat?

A: This is a 160°F (71°C) thermostat, designed for raw water cooled V6 and V8 engines to ensure they reach the correct operating temperature for efficiency and performance.

Q: OEM vs. Aftermarket?

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.