First question is which depth finder is a good one to buy that is a glue in shoot through hull??? Hawk eye seems to be the most common.
Second question is where is the sweet spot for the 25 outlaw??? I have a 2004

I installed a Airmar P79 but I also have A NMEA 2000 network and a chart plotter installed in the boat. If you think you want to go that route get a NMEA2000 capable depth transducer. Regarding installation directly beneath the motor is the best spot to install it. I did mine when I pulled the motor last year which made it a lot easier. If you think you will have to do transom work (such as steering play in the drive) I suggest wait till then and install when the motor is out. There are a ton of pics in my thread: Phil'R Up 2001 Baja 25 Outlaw
or on my Facebook page search: @iaoutlaw
but here is one of the engine bay


You can see where I sanded the bilge paint flat and installed the ring for the transducer to sit in