Pulled this out of my boat when I got it. Appears to work, but I do not guarantee it. Through hull transducer, can hear it clicking and temp changed when put in cold water. See video. 125.00 shipped, 48 States only. Can come see it or test it if you wish....denton tx. Pm me if interested.
https://m.youtube.com/watch?v=DiGR0sfovs0