Im doing a carribbean pirate game in the tradition of sid meiers pirates. In THAT game, you would buy pieces of treasure maps in taverns, and when you had all four you could see on the map where in the gameworld you should travel to find the tresure: you went there and got the treasure.

Each "rival pirate" (there were 9) could be fought and defeated and also had a treasure you could find with the above method (defeating them and finding their treasure was independant from each other.

Any ideas on how to mix this up for my game?

I want famous pirates (10-12) rooming the world that you can defeat, and maybe their buried treasure should be linked to defeating them instead of buying map pieces? Another idea is to have rumour you buy from tavern reveal different things about a treasure location, such as:

1. close to which port (eg. "close to Port Royale")
2. direction relative to that port (eg. "south-west of it")
3. Distance from that port (eg. "12 leagues from it")

Im using a simple 2d travel map as game world (satellite photo) of the carribbean which the players traverses. It's more fun gameplay to link together evidence such as those 3 above than to collect 4 map pieces and then place a marker "treasure is here" on the travel map (that feels to direct and guided).

Once you have the idea of more or less where it is, you approch the beach there. If its close enough your crew finds the treasure. If not you just leave the beach. Sp you CAN find it without the 3rd piece of information but it might be harder.

Or to get info about the treasure not before you defeat the pirate in question? (As a payment for not killing him?) Or tavernfolk only start to reveal info about the treasure after the pirate owning the treasure is defeated (since they are scared of him killing them)

I like your last idea, by giving hints or pointers to real world objects instead of a direct path to the treasure. This makes it much more rewarding, and like a real task, otherwise traveling to the treasure and picking it up might just feel like an unnecessary hassle.

But I suggest watching this video for a good analysis of a similar topic:

Thanks guys! Some good thoughts. Any more input is always appreciated.

To add to the finding mechanic, adding in something where the player has to still "find" the treasure after he has the location.

Maybe he has to dig at the right spot (maybe like minecraft digging mechanic). The player might have to look at a picture and match it to the scene he sees to locate the exact point. It could also be clues like "ten steps north from the hook shaped rock then 5 steps east" - So basically once they get to the location, there's that extra layer added to the discovery.

How about you need to combine them?

1. You collect info from romors in taverns: they guide you to the rough geographical location. "8 leagues SE of San Juan"
2. When you defeat the pirate you loot a "captains log" or "decipher key". Or simply the local map that tells the exact location of the chest buried (As Gordons suggestion, "five paces north of the large palmtree").

Both are needed to actually find the buried chest!

Fun or just convoluted?

You could start by creating a system of information as data. If you can generate a list of properties about the location where the treasure is, as well about locations leading up to the treasure, you can just toss this information randomly around people in taverns, captains, in logs, etc., and it would be up to the player to find them, and connect these data points.

I plan to work on a similar system for my game.

But generalizing it this way, you can plant these data points in any number of ways or locations. Adding a bit of story padding / tying specific characters to specific pieces of data, you could potentially generate robust quests.

I don't think it's convoluted, as long as the player understands the mechanics of finding the clues, and how to put them together. Because it's very indirect, the reward feeling could be really great.