Boats keep breaking in my canal

I have a canal that is 4 wide, and 1 block deep. The entire canal is made of source blocks and completely level. Unfortunately my boats keep breaking after only travelling a 50-60 blocks when I try to navigate the canal, and I don't really understand why.

Does my canal need to be deeper, wider? What can I do to keep boats from breaking constantly?

You have mentioned that you are on SMP so my guess is that you are lagging to the point where you bump into a wall.

A possible solution would to make the walls wider as boats are extremely fragile.

Boats are also pushed by water currents so it might keep the boat from bumping if you make water currents so I suggest that you make water flowing in the direction you want to travel rather than just creating still water everywhere.