Water Temperature Sensor – Fits Mercury/Mercruiser, Volvo Penta, OMC (Replaces 3853787, 806490T)

Water Temperature Sensor – Fits Mercury/Mercruiser, Volvo Penta, OMC (Replaces 3853787, 806490T)

This water temperature sending unit is a direct-fit replacement for a wide range of marine engines, including V6 and V8 models from Mercury/Mercruiser, Volvo Penta, and OMC that use a 3/8" NPT fitting. It is designed to provide accurate readings to your water temperature gauge.

This sensor directly replaces OEM and aftermarket part numbers: Mercury/Mercruiser 806490T / 97257A1, Volvo Penta 3853787, OMC 980613, Sierra 18-5897, Mallory 9-42400, Stewart Warner 352BC-D, Medallion A-2618-3, and VeeThree Seastar 52320S018.

• Installation Method: Installs directly into a 3/8" NPT threaded port.
• Intended Use: Functions as a sender for a water temperature gauge. Note: Not for use with overheat warning alarms.
• Durable Construction: Made from brass for reliable performance in marine environments.

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. For Mercury owners, here’s a guide to help you identify your engine’s serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

Confirm your engine model/year in the table below.

Technical Specifications

Package Contents

• 1 x Water Temperature Sending Unit (3853787/806490T)

Installation Guide

1. Ensure the engine is completely cool and disconnect the negative terminal from the battery.
2. Locate the existing water temperature sensor on the engine block, thermostat housing, or manifold.
3. Place a catch pan or rags underneath the sensor to collect any draining coolant.
4. Carefully disconnect the wire connected to the sensor's terminal stud.
5. Using the appropriate size wrench, turn the old sensor counter-clockwise to loosen and remove it.
6. Clean the threads in the port to ensure a good seal.
7. Apply a suitable thread sealant to the threads of the new sensor (avoiding the tip).
8. Install the new sensor by hand until snug, then tighten it securely with a wrench. Do not overtighten.
9. Reconnect the sender wire firmly to the 10-32 terminal stud.
10. Reconnect the battery terminal.
11. Top off the engine coolant as needed and run the engine, checking for any leaks around the sensor.

Troubleshooting & FAQ

Q: How do I confirm this sensor fits my engine?

A: First, verify that your engine requires a temperature sensor with a 3/8"-18 NPT thread size. This part is a direct replacement for multiple part numbers, including Mercury/Mercruiser 806490T, Volvo Penta 3853787, and OMC 980613. Please refer to our cross-reference and compatibility tables to confirm your specific engine model.

Q: Is this sensor for the warning alarm or the temperature gauge?

A: This sending unit is designed specifically to operate a standard water temperature gauge. It is not intended for use with an audible overheat warning alarm or system.

Q: What are the signs my old temperature sender has failed?

A: Common signs of a failing sensor include a temperature gauge that does not move, provides erratic or inaccurate readings, or is always pegged at the maximum or minimum temperature regardless of the actual engine state.

Q: What is the terminal type for this sensor?

A: This sensor features a standard 10-32 stud terminal for connecting the gauge wire.

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.