I installed a fish finder instead of trying to replace the old style with a thru hull. This Eagle model has a 120 degree scan so I get a good display of the upcoming bottom ahead, not just a reading of X number of feet in depth.
Mount the sending unit in the bow to get the best reading. I mounted the display on a swival bracket so it is out of the way when I do not need it and in good viewing when I do want to see it.