Re: Fishfinder vs depth sensor
I have used a Navman 4150 fishfinder log for about 10 years and have found it great for a small yacht.
Navman do not do marine stuff anymore but other brands are out there.
Mine was the through hull model, I have the depth in the forward area in front of the keel in silicone and the paddle wheel in the engine well.
My unit also has connections for engine hours and provides a voltage readout.
If it died tomorrow, I would try and get the same in whatever brand was similar.