Learn to "bump" the throttle. I/o's throttles tend to be too abrupt in their response, one "step" up is usually too much.
Your accelaration is due to the way an I/O planes out, as it planes it will accelerate.
Pull your rider up and accelerate hard bringing her up to plane, next, throttle back until you are one step back from where you want to be. Give her one slight "bump" up and you should be good to go.
I know this sounds funky, but it works....I spent a few years on a huge I/O with a sticky throttle, and soon enough your wrist will develop some memory.