When you have the ship hold ''A'' and press ''B'' 55x. A sliding puzzle will appear. Put the numbers in order and you win 100gp.
When you play the boat mini-game (hold A and press B 55 times on the boat to play) you will notice three seperate times on the top-right, going from lower to higher. These are times you can beat for a lot of extra cash. Here are the rewards:
If you complete the mini-game in under the time on the bottom, you get 2,000gp.
If you complete the mini-game in under the time in the middle, you get a 5,000gp.
If you complete the game in under the time on the top, you get a wopping 10,000gp!
If you don't beat any of those times, well, you get just 100g...