I am in middle of building monitor and logging system for temps now.
http://www.trawlerforum.com/forums/s...ect-36667.html
Unlimited number of sensors on bus system. With data logging. I have being running a prototype now and it interesting to review temps over time.
With exchaust mixer if your sensor is on the metal you will see a spike in temp at engine shut down as the water stops and the heat soaks into mixer from hot exhaust. While running mine sits on 37c but rises to 60c at shutdown.