Although a lot suggest blowing the sails, it would actually be better to completely lose the sails. At least where other wind can't reach. Why? Because it makes to sense to blow into sails. Sails would only complicate matters as it will interfere in most cases with your direction, making you need a large crew that sailing ships have to still float the right way as efficiently as possible.
Place the stone as close as possible to something that holds as much of the wind as possible. The further the stone is away from pushing something, the more it can be diluted or change direction from other currents. So as close as possible so it'll spent as much of it's power to thrust. If you blow it now, it'll force as much of the wind into the small solid, like a sail or just a slightly bend piece of metal. You can just place it in a box. Fix all this to something sturdy and you have all the propulsion you need. It can be anywhere in the hull, but at the center or in the front makes sense for a lot of builds. But look at cars for different effects of front or rear drive.
Now 2 ships will be created. One for speed, with a more normal hull for the period, making it aerodynamic (waterdynamic?), making it move easily through the water at high speeds. The other is simply round. Think any useful variation of a pancake with a round bottom. The stone in a box can easily be turned in these ships, giving them thrust in any desired direction. This gives them high flexibility.
Not needing a lot of sails or crew to manage it all frees up space and weight, giving you a lot of room for cargo, men or attack stuff.
The circular one could have a square on top if it's an attack ship. With 1 extra stone in a box the whole ship can rotate and keep 2 sides of the triangle at you, while pelting the enemy with all cannons. The oblique angles are perfect to make enemy cannon's have glancing blows instead of direct hits.
I could go on an on, but I'll leave the rest to you. Unless there's more questions.
Edit: @Renan gave an interesting point about placing the stone in centre mass. But if you place it behind, the front might get out of the water. This could be advantageous, as there is less water resistance and with no sails you'll not lose energy from not being completely straight.
Extra edit: the stone could be completely sealed off in a box. The wind it thrusts can be used again,making it a loop. If it actually generates wind it would need to let the air out, but this can be used in the thrust as well. You just need to be able to let it escape without pushing backwards for maximum thrust. But placing it under a boat could even be reminiscent of a jetski.