Several years ago, I had an OS-40FP and bougt TT 40GP. I got excellent much better performance from the TT engine than I did from the OS. I then bought a TT Pro46 and was amazed at the performance. I only compared it with one OS-46FX and it performed better. I will not use this to say that it is a better engine but simply to express my experience. I bought a second Pro46 and later bought a 42GP. All of the engines have given excellent service and the price is very reasonable.