When you have crew join you for a period of time, they will surely bring their personal effects with them. Inevitably they will forget something when they leave the boat and return home or onto their next adventure.
What do you do with their personal belongings that they left on your boat? Do you use them? Do you throw them away? Are you responsible for the items? What if you see them again?
In short, anything that is left on the boat when they leave is now yours to deal with. You can choose to send it to them, use it, discard it, or sell it; the choice is yours.
If you see them again, you are not obligated to give them their items back, nor are you obligated to give them cash value for their item.
Hustlers (people who try to squeeze money out of other people) will be the only people who will cause you trouble in this situation. If they leave something and you are never planning on seeing them again, why should you carry their stuff around indefinitely in the hopes that you might, by chance, meet again?
When they see you in an anchorage, they will approach you and ask you for their belongings. When you tell them that you don't have it anymore, they will begin to make a scene and try to make you feel very uncomfortable. Then they will offer you a solution to your discomfort that will make everything "seem okay": Money.
The hustler will offer you to pay them for their personal items that they left on your boat that you discarded. You don't have their items anymore, so you can't give them back, but you need your money to cruise longer and pay for things on and around the boat. The hustler doesn't care about you, they merely want your money because this is how they operate.
To quell the situation, all you need to do is recite the following:
"You abandoned the item. I salvaged the item. When you departed, our relationship ended and I owe you nothing."
If the hustler tries to talk to another member on the boat and guilts them into agreeing on a price or the payment of money, they will bring up that discussion now.
"But your wife said that you guys would give me money for it."
This is when you get to play the Captain Card!
"I am the captain, my word is the word of the boat. I didn't make any arrangements so no arrangements have been made."
At this point, they will become angry, irate, and even rude! There is no good in continuing the conversation as they won't stop until they get what they want and you aren't going to give them what they want. This is when you say:
"We're done here. There is nothing more to discuss."
They won't like this fact, but this is how the system works and they can't fight it. If they won't leave, you can always call the police to have them dealt with, but usually they will leave at this point.