The TRX Pro .15 put out about .5 bhp, so it would be advisable just to buy a new engine and go from there. I would imagine the .18CV-RX(s) would be almost a direct drop in with about 3 times the power. It wont be able to use the EZ-start, but it has a pull start. If you go the pull start route, make sure there is enough room to fit one (there should be).