You don't mention a budget so....
I've got a Lowrance Elite 4 gps/2d for the yak and a small FG boat I've got, works good, but the screen is small at 4", can't see it from a distance but in these two it's not much of an issue for me.
I've used the Lowrance Mark 5 pro on the yak but did not have gps so I got the elite 4 for the gps. the Mark 5 is a good basic FF imo, the one I had did not have gps but would assume the gps function works good.
I've currently got a Lowrance HDS 8 with SS/DS on my tracker PT175, like it a lot, but it is a bit complex to use, but it is a hi-tech FF. I've also got a HB 788 HDci (?) on the bow of the 175, the 2d FF function works good, the gps is extremely slow to boot up in the mornings, takes a long time to lock on the satelites and then when trolling at slow speed from .6 up to 1.2, the speed jumps all over the place. the only reason I have the HB on the bow or on the boat is because the transducer cable will fit on the Terrova shaft like I wanted while Lowrance tranducer cables will not fit as they are just a hair thicker.
There are +/-'s to each model or brand, go to BPS or Cabelas and punch some buttons, ask a lot of questions and read up on the one(s) you like and then go punch some more buttons and google the ones you like the best. It is a personal preference, there are two camps, Lowrance and HB,