Hi,

Haven't used a GMS 25, but i have a couple of the 47's they are alright. Produce a bunch of power when they are running right, but it is a little tricky getting them to run right in the air, they lean out a heck of a lot more than most, and seem to be much more sensitive to fuel tank position and fuel level than just about anything else.

Again don't know for sure about the 25, but most of the 47's i have seen don't turn off properly. you shut the throtle down, but it might be a couple minutes before it actually stops, potentially a big probalem for belly landing. You may go thru a lot more props. Chances are high you will spend more in the first day on props than you wil save by not buying something a little better.

Shmo