I'll add that the FL-12 & are are basically the same.Different look to the screen. Both FL-18 & 20 have the zooms.The 20 also has a day/night setting and external power posts.I never have found a use for the zoom.I've learned how to read my 8 & I keep the gain down so I see the eyes flickering in on the bottom.
Technology advances are, at the least, amazing! After reading these posts, I broke out laughing and I mean really hard. I started thinking about MY depth finder, an old Shakespear purchased in the late 1970's. The unit is handing from my garage rafter (probably with a severely corroded battery) and the transducer is somewhere on the bottom of Lake Big Sissabagama in WI. I never thought my 6 HP Merc. would have enough torque to rip the suction cup mounted transducer off, but it did.
One of those "Well, I'll be go to he**" moments!
I guess I am going to have to visit some of the mid-winter fishing/boat shows we have here to get up to speed.
If you've got short, stubby fingers and wear reading glasses, any relaxation you would normally derive from fly fishing is completely eliminated when you try to tie on a fly. ~ Jack Ohman, Fear of Fly Fishing, 1988