http://forum.shipsim.com/index.php/topic,22390.msg401678.html#msg401678
I used the keys T & Y for ahead & astern on the port outer engine, & U & I for the starb'd outer engine as Saltydog says in his second picture.
You can see from my picture below how the two outer engines are well forward of the inner ones as Mr. Robville points out, thus making them not rotatable.
Angus.