since I am using OLC's GUI for manual targetting my t/torp ratio has sunken drasticly...
In the past when I used my "uber" WO's power ti calculate the fire solution I had a 100% safety hitting the enemy where I wanted... and I know where the fuel bunkers are
One shot one kill at once was in 75% no problem and in 90% the target sunk within a "normal" time
Yesterday I attacked a convoy and shot two Empire and one liberty and only the Liberty I hit at his engines (right under the chimney) the two emipres I hit... but they steamed on like nothing... though on had a small fire..
The liberty slowed down to 2kt and was deck awashed but not sinking

I mean at this point the ship HAS to sink... 2kt and the full front under water... we're talking about a 7t ship "grinding" inteself into the waves... no result..
Shot 3 (YEAH! three!!!) torps and all hit but didn'T explode... I set the depth not deep enough caus I hiut the front part and no use...
Lesson:
manual fire I will fire two shots
I will always check the depth of my torp for ships already "partially" sinking to get the right depth or shoot an impact torp