What is the right way to attack a convoy ?

[PepsiCan]

but the fact that you have manual targetting off, doesn't mean you don't have to do any targeting.

What automated targeting does is calculate the trajectory of the fish, given your own speed, the target speed, bearing and heading etc. But you need to select the target and ensure that the computer translated trajectory gets updated so that the torpedo will take the right course.

Secondly, MK 14 torps had bugs in real life and these are mimiced in the game. The issues were
1) duds, caused by the detonator being crushed on impact with the target
2) torpedos typically ran 10 -15 feet too deep, so adjust the depth of your torp upwards (you can still influence all of this when doing auto targeting)
3) premature explosion due to a) shallow waters (see 2) and b) the wake of a previously fired torpedo setting off the detonator. this can be prevented by launching at 3-5 second intervals
4) sometimes, the torpedo gyro will be completely off and the torpedo will circle back at you and destroy you. So, after you've launched, DIVE!! (for two reasons, the enemy and your own torpedo)

All of this is simulated in the game. By mid 1943, depending on which command you belong to, the bugs on MK 14 will be fixed.

Hope this helps!