This might be discussed earlier, but here goes anyway...
When I attack a convoy and they spot me or are alerted by a torpedo explosion, all the ships start to make evasive manuevers and slow down to 5 knots. But by slowing down, they are much more easier targets, and if there is no escorts, I can spend the day by picking them up with like flowers in a meadow (

). Common sense says that the ships would hit full speed and get away from the danger. What was the historical method in these situations?
So is it possible to get the ships increase speed rather than slow down? Is there a technical restriction with this, some hard coded weird algorithm, or is this behaviour historically accurate?