[Sans Peur]

I am assuming it is an outboard or I/O. The steering will be hard on plane if the little sacrificial skeg right behind the prop is adjusted wrong (or missing altogether). This will sound counter intuitive but loosen it up (1/2 or 9/16 socket) and standing behind the engine facing towards the front, turn the skeg the same direction the steering wheel is trying to pull. You may have to move it a couple of times to get the right feel but it's not that difficult.