Thermostat Kit – Fits Volvo Penta B30 (Replaces 875791, 831040)

$24.88

Worry-free returns

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.).

You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).

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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 Thermostat Kit – Fits Volvo Penta AQ165/AQ170/BB165/BB170 Series Marine Engines (Replaces 875791, 831040) is designed for specific Volvo Penta gasoline engine models, including the AQ165A, AQ170A/B/C, BB165A, and BB170A/B/C series equipped with B30 engines, produced between 1965 and 1978. It is engineered for use in seawater (raw water) cooling systems and opens at a factory-set temperature of 55°C (131°F) to ensure optimal engine performance.

The kit serves as a direct replacement for Volvo Penta part numbers 875791 and 831040, as well as Sierra 18-3663 and other aftermarket equivalents.

Engineered for direct-fit installation.
Designed for raw water (seawater) cooled applications.
Includes thermostat set to open at 55°C (131°F).

Part Number Matrix

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

Brand	Part Number	Notes
Volvo Penta	875791	OEM Reference
Volvo Penta	831040	OEM Reference
Sierra	18-3663	Aftermarket Interchange
JLM Marine / GHmarine	875791 / 831040	Aftermarket kits referencing OEM numbers

Engine & Model Compatibility

Confirm your engine model/year in the table below.

This thermostat kit is confirmed to fit the following Volvo Penta B30 inline 6-cylinder gasoline engines:

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Volvo Penta	AQ165A	165	4-Stroke	1968–1969	875791/831040	B30 inline 6-cylinder engine
Volvo Penta	AQ170A	170	4-Stroke	1969–1972	875791/831040	B30 inline 6-cylinder engine
Volvo Penta	AQ170B	170	4-Stroke	1972–1973	875791/831040	B30 inline 6-cylinder engine
Volvo Penta	AQ170C	170	4-Stroke	1973–1978	875791/831040	B30 inline 6-cylinder engine
Volvo Penta	BB165A	165	4-Stroke	1965–1969	875791/831040	B30 inline 6-cylinder engine
Volvo Penta	BB170A	170	4-Stroke	1969–1972	875791/831040	B30 inline 6-cylinder engine
Volvo Penta	BB170B	170	4-Stroke	1972–1973	875791/831040	B30 inline 6-cylinder engine
Volvo Penta	BB170C	170	4-Stroke	1973–1978	875791/831040	B30 inline 6-cylinder engine

Technical Specs

Product Type: Thermostat Kit
Installation: Direct OEM replacement
Fuel Type: Gasoline
Housing Material: Brass/Metal
Operating Temperature: Opens at 55°C (131°F)
Engine Type: Volvo Penta B30 inline 6-cylinder
Cooling System: Seawater cooling (raw water)
Application: Marine engines

What’s in the Box

1 x Thermostat Service Kit (equivalent to 875791/831040)

Installation Notes

Disconnect the vessel's battery and close the raw water seacock.
Drain the engine block cooling system to a level below the thermostat housing.
Locate and carefully unbolt the thermostat housing cover. Note the orientation of the housing.
Remove the old thermostat and any existing gasket or sealing remnants.
Thoroughly clean both the housing and engine mating surfaces to ensure a perfect seal.
Install the new thermostat in the correct orientation.
Position the new gasket and reinstall the thermostat housing cover, tightening bolts to the manufacturer's specified torque.
Open the seacock and refill the cooling system as per the engine service manual.
Reconnect the battery, start the engine, and carefully inspect for any leaks.

Troubleshooting & FAQ

How do I verify this thermostat fits my engine?

This kit is specifically for Volvo Penta AQ165, AQ170, BB165, and BB170 series engines with the B30 inline-six configuration. Please cross-reference your engine model and year with the compatibility table. Also, confirm your engine uses a raw water (seawater) cooling system and requires a 55°C thermostat.

What are the signs of a failing thermostat?

Common symptoms include engine overheating (stuck closed) or taking too long to reach operating temperature (stuck open). You may also notice erratic temperature gauge readings or changes in engine performance.

How often should a marine thermostat be replaced?

Preventive replacement is recommended every few hundred hours or every 3-5 years, especially in saltwater environments where corrosion is more likely. Always consult your engine's service manual for specific maintenance intervals.

Is a gasket included with this thermostat kit?

This kit includes the thermostat as shown. While some aftermarket kits bundle gaskets, it is not guaranteed. We recommend purchasing the required gasket separately to ensure a proper seal during installation.

What temperature does this thermostat operate at?

This thermostat is rated to begin opening at 55°C (131°F), which is the specified temperature for the compatible Volvo Penta raw water cooled engines.

Is this an OEM Volvo Penta part?

This listing is for a high-quality aftermarket replacement, not an OEM component. It is engineered to meet or exceed original equipment manufacturer (OEM) specifications for fit, form, and function, using comparable materials. The part is manufactured in an ISO 9002 certified facility and batch-inspected for quality control.

How fast is shipping and what does it cost?

We ship worldwide, and orders typically arrive within 5–15 days for most regions. Standard shipping is free. If available for your location, expedited shipping options and costs 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 marine use. If you encounter an issue, please contact our support team with your order details. Returns are accepted within our standard return window for items that are unused and in their original condition. For detailed instructions, please see our policy page or reach out to customer service.

Safety & Important Info

Verify images and specifications against your original part. If anything differs—even if your model appears compatible—do not purchase.
This is an aftermarket replacement, not an OEM component. All mentions of brand names and part numbers are for reference purposes only.
Professional installation is recommended for safety and performance. Improper installation can lead to engine damage.

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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