Since the basis for my assertion was a poorly remembered tour of a replica of the Santa Maria, where the people running the thing mentioned that they had a motor and a GPS to satisfy the coast guard, I'm pretty sure that this is the cause. It was moored in Lake St Claire, which is between lakes Huron and Erie, so they would have had to go through the Niagara locks, the locks on the Mississippi, or through the Erie canal, both of which probably have the motor requirement.