805218T Temperature Sensor Sender for MerCruiser | JLM Marine

Temperature Sensor Sender 805218T – Fits MerCruiser 3.0, 4.3, 5.0 Engines

This engine temperature sensor sender is designed for MerCruiser inboard and sterndrive engines, providing accurate temperature readings to protect your engine from overheating. It is compatible with popular MerCruiser engine models including 3.0L, 4.3L, and 5.0L configurations.

Direct Replacements: MerCruiser 805218T, 805218 | Sierra 18-7600

• New aftermarket temperature sensor sender for reliable engine monitoring
• Direct-fit replacement for factory temperature sender units
• Easy installation with standard sensor threads

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.

Technical Specifications

Package Contents

• 1 × Temperature Sensor Sender

Installation Guide

1. Disconnect the negative battery cable to prevent electrical shorts during installation.
2. Allow the engine to cool completely before beginning work to avoid burns from hot coolant or engine components.
3. Locate the existing temperature sensor sender on your engine block (typically near the thermostat housing or cylinder head).
4. Disconnect the electrical connector from the old sensor by pressing the release tab and pulling gently.
5. Using an appropriate wrench or socket, carefully unscrew the old temperature sensor in a counterclockwise direction.
6. Inspect the sensor port threads for damage or debris and clean if necessary.
7. Apply a thin coat of thread sealant (not Teflon tape) to the threads of the new sensor to prevent coolant leaks.
8. Hand-thread the new sensor into the port clockwise until finger-tight, ensuring it seats properly.
9. Tighten the sensor to the manufacturer's recommended torque specification using a torque wrench (typically 8-12 ft-lbs).
10. Reconnect the electrical connector to the new sensor until it clicks securely into place.
11. Reconnect the negative battery cable and start the engine to verify proper gauge operation.
12. Check for coolant leaks around the sensor and verify that the temperature gauge responds correctly as the engine warms up.

Troubleshooting & FAQ

How do I confirm this temperature sensor fits my MerCruiser engine?
Verify your engine model (3.0L, 4.3L, or 5.0L) and cross-reference the OEM part numbers (805218T or 805218) with your current sensor. The compatible engine models table above provides additional fitment guidance.

What are the signs that my temperature sensor needs replacement?
Common symptoms include erratic temperature gauge readings, a gauge that stays at cold or pegged at hot, the check engine light illuminating, or engine overheating due to inaccurate temperature data sent to the ECU.

How often should I replace the engine temperature sensor?
Temperature sensors typically last 5-10 years or 500-1,000 engine hours under normal conditions. Replace immediately if you experience gauge malfunctions, coolant leaks at the sensor, or temperature-related fault codes.

Can I use Teflon tape on the sensor threads?
No, use only liquid thread sealant rated for coolant systems. Teflon tape can break off and contaminate the cooling system or interfere with the sensor's electrical ground connection through the threads.

Will this sensor work with both analog and digital gauge systems?
Yes, this sensor is designed to work with factory MerCruiser gauge systems, whether analog needle-type or digital displays, as it provides the standard resistance signal expected by MerCruiser instrumentation.

OEM vs. Aftermarket?
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.

How fast do you ship and how much does it cost?
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.

What is your warranty and return policy?
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.