The little fin will not be straight, it's all a compromise and it's normal to be hard to steer one way, the tab has to be adjusted so at normal cruise speed, the motor is kind of neutral, not pulling hard one way, you never get it perfect, but you can get it pretty good. Get the tools tools required to adjust it and take it for a run and adjust as necessary, you need to remember the tab steers the motor, not the boat, so you need to think about which way to move.