The best way to aim is at the merchents
.
Get close but not closer than 300m.
Get your bow as close to 90 degrees off targets port or starboard side.
Make sure your projected target speed is correct. I have found most merchant make about 7 kts.
Make sure your torpedo doors are open!!!! If not you will lose about 3 seconds on your calculations. Also, you are an ambush machine. Let them come to you. As you wait, get your boat into the position that best suits torpedo use and scoring!
Welcome aboard!