Right now the only way is to make alot more gold in a hurry. I have been thinking about this, and I think there should be some measures that can give a short term boost to moral. If this were real life, and the men were getting restless, but you had just gotten the last piece of the map to find Montey's hideout, you could tell them: "hey look, all you have to do is hang with me for a couple of more months and you will be richer than you ever dreamed of"
Maybe a shore leave where they all get little piece of the plunder and it takes a week of time off the game clock. This would cost you a week's (or it could be more) time, you wouldn't get any of that portion of the plunder, plus it would decrease the pot and they would get mad quicker after the effect was gone. So you are penalized for doing this if you can't make a fairly quick turn around in your fortunes.
Or, maybe there would be a way for you to enforce discipline. Once again, if it were a real life situation, there would probably be one or two of the guys who are starting to stir up all the trouble. They could confront you, and you could either choose to divide the money, or fight them in a duel for control of the ship. If you loose, they take your flagship, or you are relegated to the smallest boat in your fleet, or you are marooned if you don't have another boat. I was reading an article about Blackbeard the other day, and it told a story about him playing cards with two of his senior officers. He ended up shooting one of them in the knee, and the guy ended up with a permanant limp. Some of the other officers asked him why he had done it, and he said that if he didn't do something like every so often they would forget who he was.