Barry, I swaped out by DS for a FF
for the reasons you mention. My research tells me that a FF with a speed reading means the finder accepts input from a paddle wheel which is in addition to the depth transducer so you are still dealing with the issue of fouling the paddle wheel. I don't think the transducer can read speed from bouncing the sound waves off the bottom, though you would think someone would figure how to do this. If I am wrong someone will pipe up.I went with a Garmin 250 and got the flush mount with power/data cable package and transome mount transducer, with temp capability. SO I ended up with a flush mount in the forward cockpit/cabin trunk next to the other iinstruments. Boat has gone through a couple of sets of instruments changes, round and square cutouts, such that PO just put a 3/8th panel to cover the old cutouts and mounted the replacement instruments in the panel. Looks fine. I didn't want to haul the boat just to install a new thru hull transducer so I went with the in hull or "shoot thru hull" set up, putting the transom mount transducer in the forward bilge. you can do this if no coring i.e. air, in the hull layup. Right now the transducer sits in a baggie filled with water, works fine, until I pull the boat this winter and pull out the old thru hull transducer, glass over and permantently mount the "in hull" ducer in that spot. Note, when I get a temp reading it is basically of the hull. The Garmin 250 does not have internal battary power. With the data/power cable it is hard wired to the boat's system and you can integrate it with the other NEMA reading instruments though I am not sure what this results in, perhaps displaying the GPS data on the finder screen, speed etc., or the depth on the laptop screen. I think I paid a little over $200.FF require you to choose what frequency of ducer ( 50 or 200 or dual) and what angle of tranmission such as 20 degrees or 40 degrees, but that is another topic.