Heres some info on the IJN aerial torpedo's.
Type 91
Mod 1 17.7" diameter, 17' 4" length, 1728 lbs. weight, 331 lbs. warhead. 2000m @ 41 kts 260 kts. An older torpedo that was still being used in some land-based JNAF torpedo-bomber squadrons at the beginning of the war, including some of the units ('Nells') which attacked and sank Repulse and the Prince of Wales.
Type 91
Mod 2 17.7" diameter, 18' 0" length, 1841 lbs. weight, 452 lbs. warhead. 2000m @ 41 kts 260 kts. First deployed in April, 1941. Carried by the 'Kate' torpedo bombers which attacked Pearl Harbor.
Type 91
Mod 3 17.7" diameter, 17' 4" length, 1872 lbs. weight, 529 lbs. warhead. 2000m @ 41 kts 260 kts. First deployed in mid- to late-1942.