kamikaze ships

[Maerlyn]

do engine destroying weapons also deal damage to shields? or do they only work if the shields are already depleted?

If I use the Massive Engine Destroying Weapon found through ruins, and the enemy has got 600 shield points, will my weapon (in case it hits the target):

1. deplete the shield and deal the rest (1k -600) 400 damage to the engines?

2. only deplete the shields?

3. do nothing?

thanx