I'll throw in my experience with over 3 weeks on Lake Powell with the 9.2 foot air floor inflatable, and the Torqeedo 1003. I used the dinghy daily (OK I'll confess, I downloaded the Wall Street journal daily, except Sunday, and had to go to a place where I could have good cell phone contact to get any urgent messages about my aunt.) We used the boat for over a mile each day and at about 2 knots, we would have a 15 to 18 mile range. Slow, but not bad. Each day, my usual use was recharged by just using the 110 volt charger, plugged to the battery (on the head of the motor) thru the window of the C Dory 22, and as part of my running the Honda EU 1000 2x a day to keep the freezer and refer cold.
The engine did well for us several times when we made "potty runs" to the pump out station, and during the emergency--but during the latter we bumped the speed up to 5 knots. At this speed, the battery only had about a 5 mile range. We had to try and get to the Ranger boat, since he was not given proper directions, and ran at pretty much full speed. Even after that and over a 2.5 mile run, the battery was less than 50% drained.
So for our use, the Torqeedo 1003 gave us excellent service, and will continue to be our dinghy motor. The Torqeedo handle, has a built in GpS, gives boat speed, and range, as well as % charge, and number of watts being used.
Torqeedo makes a 40 and 80 HP electric outboard (80 hp is $20,000, and the battery is $16,000. Again, these come with the GPS technology.