Boat not being affected correctly by Rotation tag

I am making a map in which you race boats on packed ice. I wanted to have villagers in boats who would play against you. So i set up a /execute command.

/execute @e[type=!Player] ~ ~ ~ detect ~ ~-2 ~ wool 0 /entitydata @e[type=!Player,c=1]

{Motion:[0.0,0.0,0.26d],Rotation:[0f,0f]}

there is a different command for each x,-x,z,-z direction.

The rotation works with different mobs such as villagers and cows but when i place a boat down, the move but don't change their direction. Not sure if this is a bug or just how they operate thanks.