Torp speeds

[Skybird]

Bear with me, this probably got asked before, but I am late, you see, and got DW not before today noon. Search-button gave me plenty of thread pages, but I did not find what I was looking for. Only the latest partch, no mods. Need more time to work myself into LWAmi, amd wait for 3.61

I lived by the impression that when I fire Torpedos (Mk48, 688i, in this case), and set them to a lower speed (25 kn) to sneak towards their attack positions from where they should go active, that once they reach that position (activation range reached), they start to use their sensors and search for targets (in this case, active sonar/pinging preset). Once they locked onto something, they should accelerate to maximum speed 55 kn and go chasing for it.

Have I got that correct? But I have played a mission three times now, and fired multiple torpedoes that way, presets: "snapshot, depth 150-200 ft, active sonar, activation range 16K-20k yards, initial speed 25 kn". They lock onto targets indeed - but they chase for them at 25 knots, they do not accelerate.

This confuses me. I have a nice firing solution, and good timing, the fishes start locking on almost the same second when they go active, it should be almost perfect shots, no escape. Maybe I have forgotten something vital since the days of SC, or I have overlooked something in the manual? The targets turn, escape at 29-32 kn, and the topedoes go for decoys or for the targets - but always at 25 kn. Some setting I choose must be wrong!?