Car & Passenger Ferryboats
Fast car ferries operated by İstanbul Deniz Otobüsleri A Ş (known as İDO, pronounced "EE-doh") speed between Istanbul's Yenikapı Feribot Terminalı and Yalova on the south shore of the Sea of Marmara 6 times daily (more frequently in summer), making the voyage in 75 minutes, connecting Istanbul with towns in the Aegean region (map), especially Bursa.
From Yalova you can take a bus (every 30 minutes, 55 km/34 mi, less than an hour) to Bursa's main bus terminal. From the bus terminal you can take city Bus 38 or a taxi to the city center (30 to 45 minutes). More...
(Note that the passenger-only ferries plying between Istanbul's Eminönü and Sirkeci docks and Bursa's docks at Güzelyalı and Mudanya may get you to Bursa faster than the Istanbul—Yalova car ferry because the land journey is shorter, and to reach the center of Bursa you can ride the Bursaray—Bursa's metro—, avoiding heavy urban traffic you may encounter going from Bursa's main bus terminal to the city center. More...)
There are snack bars serving snacks, sandwiches, hot beverages and soft drinks on board the vessels.