"Laurie S." said:
We're mainly worried about it being a pain to attach and remove. I guess we would put it on before launching the boat? But how does it attach?
A standard fish finder will have a fixed transducer - usually attached to the transom, with a wire(s) running to the dash. The model I had on my old boat had a cradle the electronics and display plugged into - very much like an I pod dock. So, it was easy to remove, and the transducer is worth pretty much nothing, so not much temptation there for unsavory types. This is how I would go (and always have). The only tricky part is making sure the transducer is mounted correctly (they adjust somewhat), and the penetrations of the transom are sealed (wood inside of it, water penetration is a bad thing).
Portable units have a transducer that goes on a pole which clamps to something. They are designed maily for jon boats, etc. No idea how you would mount one on your boat. They are not designed for speed, so it would have to be removed before running around.
One thing to be aware of - IIRC, you have a stepped hull. So, the readout may be somewhere between noisy and useless at planing speeds. This is because your hull steps induce water under the hull for performance (lower drag), but sonar (ie, fish finders) don't read through air bubbles. Probably not a problem, since you are usually moving fairly slow when looking for fish, not flying around at 60 knots.