I am a proud owner of a 46 fx. i don't know what you've done, but mone has no hesitation when i full throttle it, and it has never once quit in the air. i have done torque rolls, and everything you can do on a trainer. i have never had any trouble with it. i run a 10x7, it seems to be an ideal prop. here's what i did to get the low end right. keep in mind i am running 15% so it has a bit more punch. the factory setting is for 10. you will have to lean it out a bit to get it to spool up seamlessly, but if you lean it out it will hesitate. i assume from the other posts that you have already richened it out. first peak it, and then turn it back to about 500 below. i don't recomend adjusting the low end while it is running. floor it really quickly and see what it does. if it is not perfect, it will hesitate nomatter whether lean or rich. but try richening it out first instead of leaning because too rich is alright, but lean is dangerous and possibly harmful to your engine. if it gets worse when you richen it, bring it back to it's origional position, and turn it the other way about 1/16 turn. it is very sensitive. keep it up until the spool up is seamless.