I recommend the Apelco (Raytheon) L365 !
I had it on my other boat and it was great !!..It has a very large screen.It has multiple mounting options. I mounted it on top of my bulkhead to the left of the companionway entrance. When I left the boat for the week, I just disconnected the cables and stored it below I would definitely use it again. It is a Combination Depth/Speed/Trip log/Temperature & Fish finder. It can set in all sorts of modes. Another very nice feature of this unit (and I expect most fishfinders) is that is will graphically show the contours of the sea bottom. It is great to show what depth is trending (getting shallow...rocks below, soft bottom, etc) it really helps with coastal navigation because you can sometimes see unique structures from the graphing capabilities and possibly pinpoint your location while moving.Try the L265 if you don't care about the speed/temp, but I think it is a great all in one unitAnd even better is is cheaper than most single function depth sounders e.g Raytheon ST-60 (Depth only!) discounts for $430 while the L365 All In One (with transom mount trandsducer) discounts for $219 !!! ($399 for Bronze thru hull version)FYI -- My new boat has all all the ST-60 instruments and they work fine (too bad no graphics) -- but for an all in one unit --you can't beat the L365