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

$16.88

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Water Temperature Sensor – Fits Mercury/Mercruiser, Volvo Penta, OMC (Replaces 3853787, 806490T) is backordered and will ship as soon as it is back in stock.

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Product Details

This Water Temperature Sensor – Fits Mercury/Mercruiser, Volvo Penta, OMC (Replaces 3853787, 806490T) is a direct replacement sender for your boat's temperature gauge. It is designed for a broad range of marine engines, including most Mercury/Mercruiser V6 & V8 models from 1988 and up, as well as specific Volvo Penta and OMC stern drives that utilize a 3/8" NPT threaded sender.

It provides a reliable cross-reference for OEM parts such as Mercury 806490T, Volvo Penta 3853787, and OMC 980613, along with aftermarket numbers including Sierra 18-5897 and Mallory 9-42400.

Installs directly with a standard 3/8"-18 NPT threaded fitting.
Engineered for use with dashboard water temperature gauges, not for warning alarms.
Durable brass and metal construction ensures longevity in marine environments.

Part Number Matrix

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

Brand	Part Number
Mercury/Mercruiser	806490T
Mercury/Mercruiser	97257A1
Volvo Penta	3853787
OMC	980613
Sierra	18-5897
Mallory	9-42400
Stewart Warner	352BC-D
Medallion	A-2618-3
VeeThree Seastar	52320S018

Engine & Model Compatibility

Confirm your engine model/year in the table below.

For Mercury/Mercruiser, this sender fits most V6 and V8 engines from 1988 onwards using a 3/8" NPT fitting. Compatibility for 4-cylinder models should be verified against your OEM part number.

For Volvo Penta and OMC, this sender is applicable to engines that specify the original equipment part numbers listed in the table.

Brand	Model	Rated HP	Stroke	Years	OEM Part No.	Notes
Mercruiser	MCM/MIE engines	V6 & V8	4-Stroke	1988 and up	806490T, 97257A1, 22-811091	For all engines using 3/8" water temp sender
Mercruiser	2.5L	4 cyl	4-Stroke		806490T	Verify application
Mercruiser	3.0L	4 cyl	4-Stroke		806490T	Verify application
Volvo Penta	Various	Various	4-Stroke		3853787	For engines requiring OEM part #3853787
OMC	Stern Drive	Various	4-Stroke		980613, 3853787	For engines requiring OEM parts #3853787, 980613

Technical Specs

Product Type: Water Temperature Sensor
Installation: Direct replacement, 3/8" NPT threaded
Thread Size: 3/8" or 9.5mm -18 NPT
Terminal Type: 10-32 stud
Temperature Range: 240° DS
Housing Material: Brass/Metal
Housing Color: Gold tone
Application: Water temperature gauge sender (not for alarm)
Compatibility: V6 & V8 engines using 3/8" NPT fitting
Usage: For marine inboard engines and stern drives

What’s in the Box

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

Installation Notes

Ensure the engine is completely cool and disconnect the negative battery terminal.
Drain the engine coolant to a level below the sensor's location to prevent spills.
Carefully disconnect the wire from the existing temperature sensor.
Using the correct size wrench, unscrew and remove the old sensor from the engine block or manifold.
Clean the threads in the port to ensure a clean surface for the new sensor.
Apply a suitable marine-grade thread sealant to the threads of the new sensor. Avoid getting sealant on the sensor tip.
Screw the new sensor in by hand, then tighten securely with a wrench. Do not overtighten, as this can damage the sensor or engine block.
Reconnect the wire to the 10-32 stud terminal on the new sensor.
Refill the cooling system with the appropriate coolant.
Reconnect the battery, start the engine, and check for any leaks around the sensor. Monitor the temperature gauge to ensure it is functioning correctly.

Troubleshooting & FAQ

How do I confirm this sensor fits my engine?

The best way is to verify your existing sensor has a 3/8" NPT thread size and to cross-reference its part number with those listed in our Part Number Matrix. It is primarily for Mercruiser, Volvo Penta, and OMC V6/V8 engines.

Is this for the warning alarm or the temperature gauge?

This is a sender for the water temperature gauge only. It is not designed to trigger a warning light or audible alarm.

What are common signs of a failing temperature sender?

Symptoms of a faulty sender include a temperature gauge that reads incorrectly (e.g., too high or too low), is pegged at one extreme, or does not move at all once the engine is warm.

Can I use this sensor for an oil temperature gauge?

While physically similar to some oil temperature senders, this unit is specifically calibrated for water temperature ranges. For accurate oil temperature readings, a dedicated oil temperature sender should be used.

Do I need to apply sealant to the threads?

Yes, applying a marine-grade thread sealant or Teflon tape to the sensor's threads before installation is highly recommended to create a leak-proof seal.

What is the difference between a sender and a sensor/switch?

A "sender" or "sending unit" (like this part) provides a variable signal to a gauge to show a range of temperatures. A "sensor" or "switch" typically operates an on/off warning light or alarm at a single, preset temperature.

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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