[Platapus]

My apologies if this does not apply to you, no offense is intended.

If you have been firing impact pistoled torpedoes in the past and now you are trying magnetic, are you switching the pistol selection switch from "I" to "M"?

You mentioned "everytime I try this, the eel sails happy directly under the target and off into the blue yonder." But you did not tell us how many times you tried this.

If you tried this once it might be a dud. If you tried this 10 times in a row and still no detonations, there might be another problem

Depending on your realism settings there will be duds, and magnetic pistols were notorious for not detonating or pre-detonating. But not every time. Your set up, as described in your original post sounds spot on.

So if your set up is OK but you are experiencing "everytime I try this, the eel sails happy directly under the target and off into the blue yonder", meaning 100% failure, this does not sound like duds. There has to be another reason.

Hence my reminder to manually change the pistol selector. Sometimes the simple stuff is what is overlooked.