OK, I know I'll probably not get an answer, since almost no-one plays Patrician 1 anymore, but here goes:

How does one manage to build new ships in this game? I try to build them, but unfortunately the game tells me that I'm missing item X or Y.
The question is: I already have the needed money and the items in the warehouse, but I stilll can't get the option to build a ship. And my old ship doesn't have the cargo hold to carry the items the shipyard is asking for.

If anyone can provide an answer to this, then thanks in advance :)

OK - Nevermind. I finally know how to do it. But here's the solution, in case someone has the same problem.

One has to sell the needed products (directly from the ship or from the warehouse) to the city, because the shipyard will get the products directly from the city in order to build the boat.