Examiners were called in to assess the bridge near the Rushcutters pub at Thorpe St Andrew at about 12:00 BST.
Train services between Norwich and Lowestoft, Great Yarmouth and Sheringham were delayed, altered or cancelled.
The Broads Authority has issued a safety warning to boat owners in light of the incident.
No injuries were reported. Those on board the 44ft (13m) Flybridge boat "Mustang" declined to comment.
The Broads Authority helped the crew on board Mustang to safety, and Norfolk Fire and Rescue Service helped secure the release of the boat.
Head of Ranger Services Adrian Vernon said it was not common for boats to hit bridges but boat owners should always check they have enough clearance to pass underneath a bridge.
Gauge boards are placed at bridges denoting their height, he added.
Abellio Greater Anglia said all train lines were open again by mid-afternoon but some services were still subject to 15-minute delays.
Alphacraft, the cruiser-hire company which owns the boat, declined to comment.
A boat caused train delays after it hit a railway bridge over the River Yare on the Norfolk Broads.