the balance point is different with every boat, but there usually somewhere between 25-35% of the boats length from the transom...with some cats the balance point is around the middle of the space between the first step and the second step. i would suggest an 8XL instead of a 7...may have less rpms, but you will be pulling less amps and it will have a little more tourque, so you can run a larger prop....i cant really tell you wat prop will work, but i would suggest getting carbon props (can be found at OSE) around the size you think will work best...(i.e. between 40mm-48mm) and test out each one....try the smallest first...if the motor is cool or only slightly warm, you can prop up...keep on using a bigger prop until the motor starts getting warm...once you find the right one, buy a metal version all balanced and sharpened up....this is a good way to find the right prop without spending a lot of money on a buch of metal props...