I'm not that great at figuring geomtery on the fly, so I dont use manual targeting.
However, in your situation, I might suggest that if your within 800 meters of your first intended target, don't fire.
There is usually another target behind or to either side. I usually target the ship behind, fire, and then target the first ship 10-15 seconds later.
If your lucky, the first torpedo will strike the ship severly damaging it, and 10-15 seconds later the second torpedo will find its target.
Provided you have enough time, target the first ship you fired upon, fire another torpedo, then fire another at the other ship.
Dive as deep as possible and turn 90 degrees and try to escape. Or sneek into the middle and make your escape then.
This don't always work, but it does for me.
But I am sure there are more experienced captians here who can offer better advice then I can.
Welcome aboard, and good hunting!
