IMHO, tower engines for the most part are junk, except for the 75, several in our club run well. If you are considering the tower 61 I would spend the extra $10 for the 75. Personally I like the FX, I have three of them and the all run great all of the time! My advice is to look at your budget, do your research, and get the engine that you like best. For the most part if you do your break-in correctly, take care of your engine, and do not run it lean trying to squeeze out that extra 100 RPM, any of those engines will make a good choice. Just my two cents.