Transporting carts by ship does not work the way it says in the english rules:

"Carts can still be carryed as freight rather than used to transport goods, but they are very heavy, weighin 40 weight units a piece."

Aside from the spelling errors, this is another thing that's in the english rules that isn't in the german ones. From my experience in the last turn (432) it doesn't work. A longboat with full crew tried to move 3 carts without further horses or riders. The weight was under the ship's capacity. Still the move command did not work, and gave the following error:

"Captain (cc01) in Azurmond - Fern Forest (-1,1): 'MOVE w w w' - The unit does not have enough coachmen or too much freights to lad the wagons."

Another typo, but that's beside the point. You apparently can not transport carts as cargo, as the english rules suggest.