Mercury - Quicksilver Engine Water Temperature Gauge Sender For MerCruiser Sterndrive & Inboard Engines 806490T. Overview. Your temperature gauge is only as reliable as the sender feeding it data. The Mercury 806490T Quicksilver Water Temperature Sender is built to keep you in the know - accurately reporting your engine's water temperature so you can spot problems before they get expensive. Designed specifically for MerCruiser sterndrive and inboard engines, this OEM sensor gives steady, true re