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

$22.49

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Thermostat Kit – Fits OMC Cobra & Volvo Penta 2.5L/3.0L (Replaces 982554, 3853799, 18-3670) is backordered and will ship as soon as it is back in stock.

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Delivery and Shipping

Free standard shipping on all orders under 1 KG

If you have any questions, feel free to email us at info@sierramarines.com, and we’ll get back to you within 20–36 hours.

Product Details

This is a direct-replacement Thermostat Kit – Fits OMC Cobra & Volvo Penta 2.5L/3.0L 120/140HP, specifically designed for OMC Cobra stern drives (1986–1993) and Volvo Penta AQ series stern drives (1986–1993) that are equipped with 2.5L and 3.0L (120-140 HP) gasoline engines. It ensures your engine maintains the correct operating temperature for optimal performance and efficiency.

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

Engineered as a direct OEM-style replacement for a hassle-free installation.
Includes a 143°F (62°C) thermostat and all necessary gaskets for a complete service.
Constructed from high-grade brass and stainless steel for durability in marine environments.

Part Number Matrix

Use this matrix to confirm equivalent references across OEM and aftermarket.

Brand	Part Number
OMC	982554/3853799
Volvo Penta	0982554
Sierra	18-3670

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For OMC Cobra applications, this kit fits 2.5L and 3.0L stern drive models from 1986 through 1993.

For Volvo Penta applications, this kit fits AQ Series 2.5L and 3.0L stern drive models from 1986 through 1993.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
OMC	Cobra 2.5L	120	4-Stroke	1986–1993	982554/3853799	Stern drive applications
OMC	Cobra 3.0L	140	4-Stroke	1986–1993	982554/3853799	Stern drive applications
Volvo Penta	AQ Series 2.5L	120	4-Stroke	1986–1993	0982554	Stern drive applications
Volvo Penta	AQ Series 3.0L	140	4-Stroke	1986–1993	0982554	Stern drive applications

Technical Specs

Product Type: Thermostat Kit
Installation: Direct OEM Replacement
Housing Material: High-grade brass and stainless steel
Temperature Rating: 143°F (62°C) opening threshold
Gasket Material: Precision-cut rubber composite
Other Technical Attributes: ISO9002 certified manufacturing

What’s in the Box

1 x Thermostat (pre-installed with sealing components)
1 x Housing gasket (314809/3852127)
1 x Ring gasket (313416/3852120)

Installation Notes

Ensure the engine is completely cool and disconnect the battery.
Drain the engine coolant into a suitable container.
Locate the thermostat housing on the engine and remove the bolts or screws securing it.
Carefully remove the old thermostat and sealing gaskets. Note the thermostat's orientation.
Thoroughly clean the mating surfaces of the housing and the engine block to remove any old gasket material or corrosion.
Install the new thermostat in the correct orientation, followed by the new gaskets as supplied in the kit.
Reinstall the thermostat housing and tighten the bolts to the manufacturer's specified torque. Do not overtighten.
Refill the cooling system with the appropriate coolant, and check for any leaks once the engine is started.

Troubleshooting & FAQ

How do I confirm this thermostat fits my specific engine?

Verify your engine model and year against the compatibility table. Cross-reference your existing part number with the numbers listed in the Part Number Matrix section. If they match, this kit is a compatible replacement.

What are the signs of a failing marine thermostat?

Common symptoms include engine overheating (if stuck closed) or running too cold (if stuck open), which can lead to poor performance, increased fuel consumption, and carbon buildup. You may also notice erratic temperature gauge readings.

Why is a 143°F (62°C) temperature important?

This thermostat is designed to open at 143°F (62°C), which is the factory-specified temperature for raw water cooled engines to operate efficiently. Using the correct temperature thermostat prevents running too hot or too cold, protecting the engine from damage and ensuring optimal fuel combustion.

Can I reuse my old thermostat gaskets?

No. It is critical to use new gaskets to ensure a proper seal and prevent coolant leaks. This kit includes all the necessary gaskets for a complete and reliable installation.

OEM vs. Aftermarket?

This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.

Shipping speed & cost?

We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.

Warranty & returns?

Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.

Safety & Important Info

Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
This is an aftermarket replacement, not an OEM component.
Professional installation is recommended for safety and performance.

About Sea Sierra

Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.

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