[KaleunMarco]

Originally Posted by Greystone

I read somewhere that to complete a patrol, one must wander around within a 200 mile radius of the "yellow star", and that, provided one does so, the patrol will be deemed complete in 48 hours.

Well, I drew the 200 mile radius & entered it on March 28 at 2100 hours. It's now April 3, 1530 hours; star's still yellow, with no notification that the patrol's been completed.
I've stayed within the circle the whole time, sunk 6 merchants on the open ocean and around 8 merchants & a couple warships in two harbors, each of which were also within the drawn circle.
Something's obviously wrong with my take on things...

ok. that's not good. each mission/patrol can have a different patrol radius...they arent all 200 miles. some are 100 miles and some are 50 miles. one has to pay attention to the orders page for this info because unfortunately most mod-sets (and stock) do not repeat that detail once you begin the patrol.
you can restart the patrol or try patrolling at 50 miles in the current one and you may see some success.
good luck. and good hunting.