I have a very nice wireless Raymarine instrument setup that includes a combination depth/temperature/speed sensor.
It's meant to be fitted through the hull and Raymanrine recommend locating it on the centreline just in front of the centreboard.
Is this advisable? Could I locate the sensor on a bracket at the stern as I have seen on a few aluminium power boats?
It is not a good idea to mount on the transom a there is too much turbulence. If you don't mind losing some range the best and safest is to mount it in a tube inside the hull where Raymarine recommend and fill the tube with castor oil or another light oil. See the article in Tips and Modifications.