How interesting. Here is a picture of the engine order telegraph from USS
Bowfin, and I don't see an "Emergency" speed setting.
As for the speed settings, I assume you mean in-game. Here is how it looks in the Gato Cfg file:
[EngineProperties]
AllStop=0.00
AheadSlow=0.40
AheadOneThird=0.57
AheadStandard=0.80
AheadFull=0.94
AheadFlank=1.00
BackSlow=-0.26
BackStandard=-0.40
BackFull=-0.53
BackEmergency=-0.66