We split our time between the gulf coast (around Tampa bay) and Key West. We are out on our TI every weekend. There are many times we end up 15-25 miles from the launch site. There have been several ocasions where the wind has died completely, or worse yet we have to fight a head wind or current to return.
The first day we had our boat we took it out in the late afternoon and went out Big pass in Sarasota (where the current is very strong), and the wind died completely. My wife and I had to pedal very hard for 2-3 hrs to get back in to the launch site (about 6-7 miles). Well needless to say I got a free ticket (from her) to buy a motor. This was in spring 2010 and the Evolve wasn't on the market yet, and all I heard were horror stories from her sister about not being able to lift and carry the two 65 lb batteries for their Minnkota trolling motor and how many times they got stranded out on lakes with dead batteries and had to paddle in (one time taking 8 hrs to paddle in on Lake Huron) on their inflatable dingy (not too smart in my opinion).
I ended up making a motor mount that fits into the rod holders (they can also be purchased (fairly inexpensive)) and mounting a 2 hp 4 stroke gas motor to the boat. I purchased the motor from a mail order place in St Petersburg,FL ( http://www.smalloutboardmotor.com/20hpo ... ecamo.html
) The motor only weighs 20 lbs and propels the loaded TI to 4 mph. The motor cost me $525 and works ok, but is not really a salt water motor so it would be a good idea if you buy one to clear coat everything before using it, and make sure you wash it off after each use (the problem is mostly all the screws and bolts, which could easily be replaced with stainless bolts for $20) . I keep mine covered when mounted. Another issue I have is if there is a lot of chop the gas sloshes around in the integrated gas tank and the motor skips once in a while (air in the fuel line), I added a fuel filter in line which seems to fix most of that problem.
Even with this 2 hp motor I feel I'm still under powered and if I were to do it again I would have either bought the small Honda 2.0 hp (which I think weighs 27 lbs), or gone up to the Mercury/Tohatsu 3.5 hp (which I think is around 37 lbs), I think they are around $900 but I think are much more powerful and more reliable especially in salt water (kicking myself now that I settled for something less). If you can find a used 2 stroke (nobody makes new 2 strokes anymore (pretty much banned)) like a 3.3 Merc grab it, they are great motors and last forever and are much more powerful and lighter than anything new. Be careful though 2 strokes are being banned at a lot of places these days.
I only use my motor for emergencies, but always have it on the boat (just in case) and always carry 40 miles of fuel (1 gallon). I've had the motor now for a yr and a half and total spent on fuel to date is around $12 bucks.
There are a couple TI's out there with Evolves now, I am waiting to hear reports on speed and duration. Hope this helps