[peterloo]

Get close to the target ship before you fire (< 2000m)

If you are too far away, the probably of hit will be low and you will waste a lot of rounds

Also, be careful,

1) Check the state of the nationalities (hostile? friendly? neutral?)

2) Hostile mechants will call in help once you hit them, and destroyer and air support comes in quickly once their SOS signal is given out... Shooting the target ships takes much longer time than before (due to GWX, which reduces half of desk gun damage), so it may not be a good idea to do so

If I were you, I would send each ship 1 torpedo (or 2 for the dud settings)
After damaging them, surface, get close and open fire