When mine carts go next to boats they pick the minecart up. Funny, but annoying!

We have an aqueduct running next to a rail track on our server. The rail is immediately adjacent to the water. The aqueduct is 2 blocks wide so the boats have to, by definition, be in a block next to the edge. Our rail runs along both sides of the aqueduct (down and back). Whenever the minecart comes past a boat it picks it up (including sometimes the person in the boat!)

I wouldn't expect the minecart to pick up the boat unless either the cart was in the water or the boat were on land. I have noticed that when you run the boat all the way to shore it does overlap the shore block, and if you are near the shore sideways the oar does reach land, so maybe it's got to do with the large hitbox?