i've noticed that it doesn't always work. they'll start heading on course. I'll recall way do some work, come back and my boat isn't even on the right side of the map?!?!? that's what I get for having a Female Tillerman....
Now, that is the ultimate in either efficiency or laziness? If I were the Tillerman/Pilot and my Captain left the ship, I would sail where ever I pleased because he is not around to monitor my course. Even if you plot a course on a World map and give it to the Tillerman/Pilot, the Ship will stop if they run into a Dolphim, Water Elemental, some fish someone threw over-board, or whatever. A real Ship, especially the Orc Ship should just plow thru those objects like they were paper!
Note: Not sure if people are aware of this: The player crafted World Maps are a lot larger and easier to plot courses on then the NPC purchased ones.