why not just make one square bounding box instead of having it the exact dimensions of the boat? if it's a square on the X and Y (forward/backward, left/right), and the height of the boat on the Z (up/down), I know it would make the collision a little funky when it's wider than the boat, but it wouldn't make any more problems than what there is now, and it would be a damn sight less confusing, being able to go though tight spaces one way, but not the other.