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

$19.97

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Thermostat Kit – Fits OMC Cobra & Volvo Penta 4.3L-5.8L V6/V8 (Replaces 383307, 18-3653, 3856961) is backordered and will ship as soon as it is back in stock.

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You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).

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Product Details

This Thermostat Kit – Fits OMC Cobra & Volvo Penta 4.3L-5.8L V6/V8 (Replaces 383307, 18-3653, 3856961) is a 160°F thermostat kit designed for a wide range of OMC Cobra and Volvo Penta sterndrive applications. It is engineered for V6 and V8 engines from 3.8L to 7.5L, covering models manufactured from the 1970s through the 1990s.

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

Engineered for direct replacement installation.
Maintains a 160°F (71°C) operating temperature for optimal engine performance.
Includes necessary gaskets and an O-ring for a complete installation.

Part Number Matrix

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

Brand	Part Number
OMC	379754
OMC	383307
OMC	3856961
Sierra	18-3653
Sierra	18-3554
GLM	13430
GLM	13060
Mallory	9-43156
Mallory	9-43021
Volvo Penta	3856961

Engine & Model Compatibility

Confirm your engine model and year in the tables below to ensure proper fitment.

For OMC Cobra sterndrives, this kit is compatible with various models from 90 HP up to 7.5L engines, spanning from the 1970s through the 1990s.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
OMC	90	90 HP	4-Stroke	1970	379754/383307
OMC	100	100 HP	4-Stroke	1972–1973	379754/383307
OMC	120	120 HP	4-Stroke	1969–1980	379754/383307
OMC	140	140 HP	4-Stroke	1973–1980	379754/383307
OMC	155	155 HP	4-Stroke	1969–1972	379754/383307
OMC	165	165 HP	4-Stroke	1972–1976	379754/383307
OMC	170	170 HP	4-Stroke	1974	379754/383307
OMC	175	175 HP	4-Stroke	1975–1977	379754/383307
OMC	185	185 HP	4-Stroke	1978–1980	379754/383307
OMC	190	190 HP	4-Stroke	1974–1977	379754/383307
OMC	200	200 HP	4-Stroke	1979–1981	379754/383307
OMC	210	210 HP	4-Stroke	1969–1972	379754/383307
OMC	215	215 HP	4-Stroke	1971	379754/383307
OMC	225	225 HP	4-Stroke	1971	379754/383307
OMC	230	230 HP	4-Stroke	1979–1981	379754/383307
OMC	235	235 HP	4-Stroke	1971, 1975–1977	379754/383307
OMC	240	240 HP	4-Stroke	1978	379754/383307
OMC	245	245 HP	4-Stroke	1972–1975	379754/383307
OMC	250	250 HP	4-Stroke	1970–1973, 1979	379754/383307
OMC	260	260 HP	4-Stroke	1979–1981	379754/383307
OMC	305	305 HP	4-Stroke	1977–1982	379754/383307
OMC	350	350 HP	4-Stroke	1977–1982	379754/383307
OMC	454	454 HP	4-Stroke	1977–1982	379754/383307
OMC	3.8L	3.8L	4-Stroke	1981–1985	383307
OMC	4.3L	4.3L	4-Stroke	1985–1986	383307
OMC	4.3L	4.3L	4-Stroke	1994–1997	3856961	4.3L and 4.3HO
OMC	5.0L	5.0L	4-Stroke	1982–1988, 1994–1997	383307/3856961
OMC	5.7L	5.7L	4-Stroke	1982–1988, 1994–1997	383307/3856961
OMC	5.8L	5.8L	4-Stroke	1994–1997	3856961	Includes 5.8EFI
OMC	7.5L	7.5L	4-Stroke	1982–1988	383307

For Volvo Penta engines, this kit fits specific GL, GS, Gi, FL, Fi, and FSi series models—verify your part number (3856961).

Brand	Model	Rated HP	Stroke	OEM Part No.
Volvo Penta	4.3GL	4.3L	4-Stroke	3856961
Volvo Penta	4.3GS	4.3L	4-Stroke	3856961
Volvo Penta	4.3Gi	4.3L	4-Stroke	3856961
Volvo Penta	5.0FL	5.0L	4-Stroke	3856961
Volvo Penta	5.0Fi	5.0L	4-Stroke	3856961
Volvo Penta	5.7GL	5.7L	4-Stroke	3856961
Volvo Penta	5.7Gi	5.7L	4-Stroke	3856961
Volvo Penta	5.8FL	5.8L	4-Stroke	3856961
Volvo Penta	5.8Fi	5.8L	4-Stroke	3856961
Volvo Penta	5.8FSi	5.8L	4-Stroke	3856961

Technical Specs

Product Type: Marine Engine Thermostat Kit
Installation: Direct Replacement
Temperature Rating: 160°F (71°C)
Connection: O-ring Seal
Housing Material: Brass/Bronze
Operating Temperature: 160°F (71°C) Opening Temperature
Warranty: Standard Manufacturer Warranty
Other Technical Attributes: Includes gaskets and O-ring for complete installation

What’s in the Box

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 Notes

Ensure the engine is completely cool and disconnect the battery terminals for safety.
Drain the engine coolant to a level below the thermostat housing.
Loosen the hose clamps and remove the coolant hoses connected to the thermostat housing.
Unbolt and remove the thermostat housing cover. Note the orientation of the old thermostat.
Remove the old thermostat and discard the old gaskets and O-ring.
Thoroughly clean all mating surfaces of the housing and engine block to remove old gasket material and corrosion.
Place the new thermostat into the housing in the correct orientation.
Install the new gaskets and O-ring as required for your specific model.
Reinstall the housing cover and torque the bolts to the manufacturer's specified value.
Reconnect hoses, refill the cooling system with the appropriate coolant, and reconnect the battery.
Start the engine and let it warm up, checking carefully for any leaks around the housing.

Troubleshooting & FAQ

How do I know if my engine thermostat is failing?

Common signs of a faulty thermostat include the engine overheating on gauges, or conversely, running too cool and not reaching its proper operating temperature. You might also notice coolant leaks around the thermostat housing.

Is a 160°F rating correct for my marine engine?

Yes, a 160°F (71°C) thermostat is the standard temperature rating for most raw-water cooled sterndrive and inboard marine engines like those listed. It provides the right balance for efficient combustion and prevents salt and mineral crystallization.

Why does this kit have 5 pieces while others only have 3?

This comprehensive kit includes two additional gaskets (OMC 314809 and 313416) to cover a wider variety of OMC and Volvo Penta housing designs over the years. You will only use the thermostat, O-ring, and the specific housing gasket that matches your engine's configuration.

Do I need to use a sealant on the gaskets?

Generally, new gaskets are designed to seal without additional sealant. However, a light, non-hardening sealant approved for marine use can be applied to damaged or pitted surfaces to ensure a leak-proof seal. Always consult your engine's service manual for specific recommendations.

What is the difference between an OEM and an aftermarket part?

This listing is for a high-quality aftermarket replacement part, not an original equipment manufacturer (OEM) component. It has been engineered to meet or exceed OEM specifications using comparable materials. Our parts are made in an ISO 9002 certified facility and are batch-inspected to ensure quality and consistency.

How fast do you ship and what does it cost?

p> We ship worldwide quickly. Typical transit time is 5–15 days for most regions. Standard shipping is free, and expedited shipping options, where available, will be presented at checkout.

What is the warranty and return policy?

This product is covered by a 1-year warranty against manufacturing defects under normal operating use. If you encounter any issues, please contact our support team with your order details. Returns are accepted within our standard return window for unused items in their original condition. See our full policy page or contact us for instructions.

Safety & Important Info

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

About Sea Sierra

Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and rigorously tested for real-world reliability.
Fast Global Fulfillment — We offer free standard delivery to most regions with a typical transit time of 5–15 days.
Manufacturer-Direct Value — By working directly with manufacturers, we provide fair pricing without compromising on materials or quality control.

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