Although the supply of doubloons is meager in the early trading, you get more of them and get them faster as the game progresses. You will seldom be stuck with the same ship for more than a few days (dockings).
You will need the largest ship, the Phoenix Warbird (1 million doubloons), to have any chance against Captain Crawfish, and having the skilled Cannoneer will improve your chances.
(see related question)
You will need to amass your doubloons to buy larger ships, because only the largest, the Phoenix Warbird, stands a chance against Captain Crawfish. (see related question)
All of the ships larger than the raft have cannons, but you need the biggest ship, the Phoenix Warbird, to beat Captain Crawfish. As you can afford each larger ship, trade up to get cargo and doubloons faster.
He has a Phoenix Warbird. You can buy one just like it to battle him, but it costs 1,000,000 doubloons. Start by buying a small ship and work your way up, because you can earn more doubloons with a larger ship.
After you collect all 5 map pieces, the new island (Skullduggery) appears near the Pirate Outpost. But there is nothing you can do there right away. You have to continue to accumulate doubloons, so that you can buy a ship that can beat Captain Crawfish. You need the largest ship, the Phoenix warbird, and the skilled crewmen: the Shipwright and the Cannoneer. Once you defeat captain Crawfish, return to Fort Ridley and the governor will give you the directions to the buried treasure on the small island.
Nothing. Captain Crawfish was there. But you don't exactly do anything on Skullduggery island. You defeat Crawfih on sea.
There is nothing to do there until you defeat Captain Crawfish. Get larger ships as soon as you can to raise 500,000 doubloons toward the 1,000,000 you need to get the Phoenix Warbird. (You can borrow another 500,000 at the Golden Harbor Bank, but don't get sunk with them aboard!) After you defeat Captain Crawfish, go back to Fort Ridley and the governor will give you a shovel and a map to the treasure on Skullduggery. You can go there and dig it up.
You buy larger ships from the shipbuilders at Dragon Cove. When you first get the raft, you need to raise 3000 doubloons to buy the smallest ship. You can do this by salvage or by trade. As you get larger ships, you earn doubloons faster.
Yes. Until you defeat the Captain, the governor will not give you the directions to the treasure buried on Skullduggery.
When you have the 5 map pieces, another small island appears on the map near the Pirate Outpost. But you can do nothing there until you defeat Captain Crawfish. Keep collecting doubloons and salvage, and buying new ships and crew, until you have the biggest ship, the Phoenix Warbird, and the Shipwright and Cannoneer. With these, you can defeat Captain Crawfish and the governor will give you the map to the buried treasure on Skullduggery.
There is nothing to be found on the hidden island (Skullduggery) until after you beat Captain Crawfish. After you defeat Captain Crawfish, the governor gives you a treasure location and a bone shovel. Sail to the hidden island. You will find the treasure under a mound, six paces right from the pirate flag.
You have to get a lot of doubloons to get the Phonix Warbird by beating other ships so you can get a lot of doubloons from them. When you have about 500,000 you can loan another 500,000 from the bank and buy the phonix Warbird and to beat him fast you chase him around skullduggery island and then when your on the side and captain crawfish is on the other and you are anchored then you have to shoot him repeatedly so you can beat him.
The 5 map pieces, when assembled, shows a new island, called Skullduggery, near the Pirate Outpost. But you cannot do anything there right away. You still have to amass doubloons to buy larger ships, so that you can fight Captain Crawfish. To win, you need the Phoenix Warbird, the Shipwright, and the Cannoneer. Once you defeat Captain Crawfish, you can get the treasure map from the governor on Fort Ridley.