The quest that is repeatable is called Cuergo's Treasure Map. It can all be done in South Western Tanaris.
Lost Rigger Cove is south of Steemwheedle Port. It's full of pirates that drop pieces of a map. Middle, Lower, and Upper. Once you have 3 you can right click one and form a map to start a quest.
http://www.thottbot.com/?i=13965
Grind the pirates, when you have a decent amount of maps go to 53,94 and look for the half sunken pirate ship along the coast. Once you click it, a chest will pop out and 5 mid 40s pirates will pop out. Kil them all, loot the key, and open the chest for your items and xp.
Here's where you can repeat it. If you have a few maps, RIGHT AFTER you loot the chest you can make a new map. This time you won't have Cuergo's Key. Run about 4 screens away, around the mountain which adds up to about 15 seconds of running away. Then run back. The pirates you killed should now be lootable again. The only loot there will be the key, then you can go back to the chest.
For the mast to reset it takes about 5 minutes. You'll also have to kill the 5 pirates again. Once it's reset, start the quest again. This skips the wait and you can just keep handing them in. Remember, once you hand one in, run away, run back, loot, then turn in.