Why does my boat turn all the way to the left but not turn right?

Several solutions: 1) If the steering cable is hitting the port side well instead of going into the steering recess, it will stop the cable. 2) Someone has bent the cable ram where it goes through the tilt tube of the motor. (This is assuming that you are saying that the front of the motor goes to the left, which is in fact a right turn, and not completely to the right, which would be a turn to port). Turn helm all the way for a right turn, which extends the steering ram on the port side of the engine. Lay a straight edge on the ram. Check for straightness. If it's bent, install a new steering cable. I have seen bad mechanics straighten the rams, but you are playing with people's lives here. do it right or not at all. You can disconnect the steering ram link to the motor at the steering cable, turn the motor right and left without moving steering cable. This tells you it's in the steering or the motor, (if motor won't turn lock to lock). Good luck.