Continuity mistake: During the bear in the cabin scene, after Chet puts the door back up, shortly after, you'll see the door is on the floor while Roman is fighting the bear with the oar from the steps. (Also, note in that same shot, you'll see the bookshelf was destroyed to pieces with its books all over the floor. That scene was never shown and must have been cut from the movie).
Continuity mistake: The scene where John Candy gets the recently rented speed boat stuck in the gates precedes the scene where Dan Ackroyd actually chooses the boat. This is also confirmed as Buck asks his dad if he can go off on his own while the speed boat is being chosen, but in the scene when the boat is stuck only the youngest son is in the back of the car.