I use T,Y,U & I as the keys for this purpose. (coming from the top downwards in Saltydog's picture) T for port outer ahead, Y for port outer astern, U for starb'd outer ahead & I for starb'd outer astern. You can of course use any keys you wish but assign them to the four listed controls which Saltydog shows.
Thanks Salty for pointing that out, it does make controlling her engines much easier.
Angus.