[Strategia_In_Ultima]

That's because the movement ability only grants movement points, not defense. Also, ships move one side at a time and remain still for as long as another side's ships move. (Yes I know, but it's how the game works.) On their next turn, they might move in an entirely different direction, or in the same direction but less distance, so the "speed" of the previous turn imparts exactly nothing on the ship the next turn.

There are however at least several mods who adress this, by giving engines a defence bonus ability. Btw..... I always thought the highest-level defence bonus of a component in the same family worked on a ship? So the bonus won't stack, right?