I've been working on this kind of stuff for 3-4 yrs now and have researched out the Evolve for use on my TI. I'm a Watertriber and wanted to enter the Watertribe EC challenge 300 mile race in Florida in their class VI (experimental electric class). I worked out all the calculations as far as run time power consumption, etc and came up way short. I would need 50-60 hrs of continuous power (about 200 watts) in order to average around 4mph for the whole race. Even with twin solar panels, and a fuel cell (which I developed for the event), I still came up short.
Actually there was a guy entered in the EC challenge 2 yrs ago with a Windrider 17 and a torqeedo 403 motor (same motor used in the evolve) with duel batteries and a solar charging system, I believe he ran out of juice and gave up. Of course this is my interest area so we talked quite a bit before the race. I knew (from my own research) that he wasn't going to make it even before he started, especially with a huge 450 lb tri that is a bear to paddle.
The Evolve system is without a doubt the best system available today bar none for electric propulsion. If I still owned a revo or Oasis and wanted to have some back up propulsion for venturing off shore a little further than what would be normal I would definitely have on stored in my hatch for emergency.
Where we typically go down in the keys it is very dangerous venturing too far with fierce currents that will get even a stock TI into trouble unless it is specially hardened for far offshore use, and can't overcome the strong currents and trade winds, which can be a handful if in the wrong direction (definitely not for the faint of heart, and boy do you have to know the waters well with adequate shore support (help when you need it), or else next stop Cuba).
I'm with Chopcat on this one, here is a breakdown of the costs.
Evolve V2 $2099
Spare battery $720
Solar charger $620
Average power sailing speed 4-5mph
range about 20-30 miles (way less if in emergency situation)
Single Honda 2.3 gas engine $950
PVC motor mount (home made) $30 bucks
Gas (about a dollar a day to operate)
Annual cost (sailing once per week) $1032
average sailing speed 6-8 mph
range 150-200 miles (carrying 2.3 gallons of fuel on board, 14 lbs of fuel)
Duel Honda 2.3 gas engines ($950 x2) $1900
PVC motor mount (home made) $35 bucks
Gas (about a dollar a day to operate)
Annual cost (sailing once per week) $1982
average sailing speed 8-10 mph (hopefully eventually I hope to average 10-12 mph once minor tweaks are completed). So far fuel consumption remains about the same as with the single motor (obviously you use more fuel per hr with twin engines (not double, about 1.25 times more fuel so far, but additional testing is needed), but your going twice as fast so MPG actually increases)
range possibly 200 miles (still needs testing) with 2.6 gallons of fuel on board (17 lbs of fuel)
The Honda weigh 27lbs ea and are extremely compact and easy to carry if needed ( I keep mine permanently mounted on my TI on the trailer (the motors have never been removed)
Here is a pic of my duel Honda's
The duel engines is probably overkill, a single engine setup is way more than adequate.
Here is an old video of my single engine setup (previously posted)
Here is a video of my duel engines in action
Of course most of what I have is overkill, we are scuba divers and often go offshore (mostly around Key West), I have the boat specially hardened for offshore use with massive sails and hull re-enforcements, along with radios, flares, full nav lights, life raft,
With my setup I get 75-100 miles per gallon fuel consumption consistently (fuel consumption average still holds after a yr and a half of continuous use). Of course to get that type of economy you have to pedal 100% of the time, and also keep your sails working as efficiently as possible (even when under power). With two strong peddlers fuel economy increases even more.
I have to admit the Honda engines far exceed any of my expectations as far as quality and reliability, I'm sure other brands are equal, I just happen to have selected a Honda, after wearing out my first (not a Honda) motor after 3 yrs of use on my TI.
At the really low throttle setting that I use (under 1/4 throttle) the Honda engines are extremely quiet and you can easily talk over them. Basically I go out sailing every weekend and have lots of fun for under a buck in fuel per week. Of course if you have enough wind you just tilt them up and don't use them.
Realistically we don't notice much if any speed degradation if we have 1, 2, or even 3 200 lbs adults on board. The boats sails just fine, we only notice a slight speed loss when we have 4 or more people on board. So in the mix of things another 30 lbs (or 60 lbs with duel engines) in the boat means absolutely nothing.
Hope this helps you