I've also got the Easy Troller with hydrofoil fins on a Honda BF-90 4 stroke on an 18-ft Alumacraft Magnum 175cs. Since my boat is a little bow light, the fins help with control and planing quicker at low speed. Seems to run nice at high speed too. At first I thought it took about 2 mph off my top end speed(about 33-34 mph before), but I found that if I adjusted the tilt up a little bit (which I normally run all the way down at high speed), I found a sweet spot where I got most of the speed back, maybe I lost 1 mph. All in all, I'm very happy with it, just wish I could get up to Winni soon...

Another thing, it definitely helps in trolling in rough water as others have posted.