Oh, LOL memories.
Back when SH3 was first released a cheat application was designed, commonly called a Game Trainer. Basically it offered instant reloads, unlimited ammo and nuclear explosions. Various sites still have this tool but it is highly unlikely that it will work with any supermod without adverse effects.
Today, S3D is our tool. With a little knowledge and patience, you can increase torpedo speed, number and damage radius. The same is true of other types of ammo.