Some of them are indeed tough, but the good thing about boat orders, is that individual, completed boxes will still give you a reward even if the rest of the boat order hasn’t been completed! Besides, if you feel like you won’t be able to complete a boat order, you can always send the boat away (before completing any box) and start working on the following one. Just tap on the "boat" icon below the ‘order reward’ as soon as the ship arrives at your dock.
If you need help completing a tougher order, you can ask your friends for help by tapping on the "ask for help" button on the boxes you won’t be able to complete yourself. You can also purchase items you don’t have time to produce by searching through your friends’ roadside shops and the newspaper. Boats are a challenging part of the game, and completing them is always a great satisfaction!