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....

Not sure if this is what you're looking for.

http://www.scriptuo.com/index.php?topic=2909.0

The Shrine in Covetous  gives you a map so you can find 'Corgul the Soulbinder'.

Corgul resides on a mysterious moving island. To reach him, you must first go to the second level of dungeon Covetous and sacrifice a used or unused Treasure Map as well as a World Map (NPC bought or player-crafted). Upon sacrificing the items, a new map will be placed in your backpack with the location of the Island of the Soulbinder where Corgul roams. Your hit points will also be reduced to 1 as a blood cost. Be careful not to die to any monsters before you can heal up. All party members must have the High Seas expansion and the party must approach the island on one of the High Seas boat types or the island will not be accessible.

Take the map and get on a ship. You can either sail to the location manually or drop the map on a tillerman, say "start" and he will sail the ship for you.