First you have to makes sure that Killer Sub will work with your version of the game. there were four patches issued, then Silent Hunter 4 U-Boat Missions which constitutes patch 1.5. You have to identify what level you are at. You really should be at 1.4 if you don't have SH4UBM, which is a $10 download giving you a lot of additional game functionality.
Then check out Killer Sub, which may only be good for 1.3. I know it is a very old mod. If not compatible, check out SilentFire mod, which works in 1.5 and maybe 1.4.
Of course I have my subnuclear series. I'm working on a new deck gun because I'm not satisfied with the range adjustment on the Subnuclear Real Deck Gun. I think I'm just going to modify the present deck gun and put that out there too. In addition I have the Subnuclear Mark 14 and soon the Subnuclear Cutie. Actually the Cutie is done but not published. I'm a lazy sort.
