Milazzo in two hours
What you can see if the hydrofoil is close and the castle is not.
Stay on the level
Two hours are enough for Via dei Mille, the port and Marina Garibaldi, with a look at the old town. They are not enough for the citadel and the cape together. The detailed itinerary is in the Milazzo guide.
If you have a ticket in your pocket
Walk back to the piers with margin. The real time is the company’s, not an estimate on this site.