Mercury MerCruiser — Water Temperature Gauge Sender — 806490T
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Mercury MerCruiser Water Temperature Gauge Sender 806490T
The Mercury MerCruiser 806490T is a genuine OEM engine water-temperature gauge sender for applicable MerCruiser sterndrive and inboard engines. It uses 3/8-18 NPT threads and sends engine temperature information to the helm gauge. This is specifically a gauge sender, not the separate coolant-temperature sensor used by the engine-management system.
Compatible Applications
- 4.3L V6
- 5.0L V8
- 5.7L / 350 V8
- 6.2L V8
- 7.4L / 454 V8
- 8.1L inboard
- 350 MAG, 377 MAG, and Scorpion applications
Mercury's Quicksilver catalog broadly identifies 806490T for MCM sterndrive and MIE inboard engines. Confirm your engine serial number and parts diagram before ordering.
Part Details
- Part number: 806490T
- Full service number: 87-806490T
- Brand: Mercury Marine
- Official product type: Water temperature gauge sender
- Thread: 3/8-18 NPT
- System: Engine cooling / instrumentation
- GTIN: 745061495128
Related Parts
- 49734 — Dual-station water temperature sender
- 805218T — Coolant temperature sensor (separate function; see Serial Number Fitment Notice)
Serial Number Fitment Notice
Some MerCruiser engines use both the 806490T gauge sender and the 805218T coolant-temperature sensor in the same cooling system. These parts perform different functions and should not be interchanged.
When This Part Needs Replacement
Replace the sender when diagnosis confirms an inaccurate, intermittent, or non-functioning temperature-gauge signal, or if the terminal, threads, or sender body are damaged.
Installation Notes
Allow the engine to cool before removal. Install the sender in the specified cooling-system location using the correct service procedure for a 3/8-18 NPT sender. Reconnect the gauge wiring and verify normal temperature-gauge operation after installation.
Alternate/Superseded Part Numbers
- 806490T — current OEM number
- 806490 — superseded
- 97257A1 — superseded
- 97257 — earlier reference
- 36525 — earlier reference
Technical FAQ
Is this the same as the coolant-temperature sensor? No. This part drives the dash temperature gauge; the ECM coolant-temperature sensor (805218T) is a separate component with a different function.
How do I know if this is the right sender for my engine? If you are unsure, confirm the engine serial number against your parts diagram, since exact fitment depends on engine model and serial range.
Parts Desk Insights
Best use case: This sender is the right part when the helm temperature gauge is reading inaccurately or not at all, and the diagnosis points to the sending unit rather than the gauge or wiring.
Common mistake: The most common mistake is confusing this gauge sender with the ECM coolant-temperature sensor. They look similar and sit in the same cooling system, but only 806490T drives the dash gauge.
Sizing and fitment: If you are servicing an engine that uses both a sender and a sensor, confirm your engine serial number and diagram position before ordering to make sure you're replacing the correct one.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 1-3 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
We are serious about product integrity — and equally serious about taking care of our customers. If there is ever a product issue, contact us immediately so we can make it right.
For return authorization, please contact our support team before shipping anything back.