Thermostat Kit – Fits OMC Cobra & Volvo Penta 2.5L/3.0L 120/140HP (Replaces 982554, 3853799, 18-3670)

Thermostat Kit – Fits OMC Cobra & Volvo Penta 2.5L/3.0L 120/140HP (Replaces 982554, 3853799, 18-3670)

This marine thermostat kit is designed for OMC Cobra stern drives (1986–1993) and Volvo Penta AQ series stern drives (1986–1993) equipped with 2.5L and 3.0L (120-140 HP) gasoline engines.

It serves as a direct replacement for OMC part numbers 982554/3853799, Volvo Penta 0982554, and Sierra 18-3670.

• Opens at a precise 143°F (62°C) to regulate engine temperature.
• Includes all necessary gaskets for a complete, leak-free installation.
• Constructed from high-grade brass and stainless steel for corrosion resistance and durability.

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 (pre-installed with sealing components)
• 1 x Housing Gasket (Replaces 314809/3852127)
• 1 x Ring Gasket (Replaces 313416/3852120)

Installation Guide

1. Ensure the engine is completely cool before starting.
2. Drain the engine coolant to a level below the thermostat housing.
3. Locate and carefully remove the bolts securing the thermostat housing cover.
4. Remove the old thermostat and gasket, taking note of its orientation.
5. Thoroughly clean the mating surfaces of the housing and its cover, removing any old gasket material.
6. Install the new thermostat, ensuring it is seated in the correct direction.
7. Position the new housing gasket and reinstall the cover. Tighten bolts to the manufacturer's specified torque.
8. Refill the cooling system with the appropriate coolant mixture.
9. Start the engine, allow it to reach operating temperature, and carefully check for any leaks.

Troubleshooting & FAQ

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

A: This kit is designed for OMC Cobra and Volvo Penta 2.5L and 3.0L (120-140 HP) stern drive engines manufactured between 1986 and 1993. The best way to confirm fitment is to match your old part's number to one of the cross-reference numbers: OMC 982554/3853799, Volvo Penta 0982554, or Sierra 18-3670.

Q: What are the main symptoms of a faulty thermostat?

A: Common signs of failure include engine overheating, the engine failing to reach normal operating temperature (running too cool), erratic temperature gauge readings, and coolant leaks from the thermostat housing area.

Q: What is the operating temperature of this thermostat?

A: This thermostat is calibrated to begin opening at 143°F (62°C). This ensures your engine warms up correctly and maintains a stable temperature for optimal performance, fuel efficiency, and longevity.

Q: Is this an OEM or 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.