As easily said as done. You avenge the Furlbrows, then send the ship to a watery grave when it goes the other way down Westfall's coast. You return to Sentinel Hill yet again to find the King of Stormwind there. Apparently the ship's mission was the blow up the capital of Stormwind, and it succeeded. Now Sentinel Hill is the capital, thanks to your technological innovation. Stormwind will be rebuilt, and it'll all be thanks to you.
A job well done.