Webster

one thing to remember if you use auto targeting, the torps will almost always hit the exact same spot every time so its best to fire one then on the next torps you lock, unlock, move the crosshairs forward or back from the centered auto lock position and fire. that way you aren't hitting an already destroyed section over and over wasting torps. you have to lock first then unlock or it wont aim right.

another tip is if you fire one torp and wait for a result it takes more torps to sink that ship because the game simulates "damage repair" between torps. what that means is, if a ship would sink from 2 torps fired at the same time (even at the same spot) it will take 3,4 or even 5 torps to sink if you fire, wait to see what happens, and then fire again.

I have a torpedo testing mission in my torpedo mods you should use and practice sinking stationary ships to see how many torps each takes to sink and how different the results are if the aiming point gets changed after the first torp is fired. you might also like to use the mod itself to increased torp power the mod gives you