It makes little sense as to why you want to be able to shoot harder.
It isn't as if a guy is more attractive/appealing/better in bed based on his ability to shoot hard/far.
But yes, kegel (muscle) exercises may do it for you, I used to do them for kicks, but for the purpose to be able to control my orgasms better. But that is another story.
You can probably find out kegel exercises easily online, but one such exercise, is when you are urinating, forcibly stop yourself midstream and hold it for a few seconds, and let go. Repeat.