I've noticed a recurring problem whenever I play Civ V. I usually send out one or two Scouts to explore and upon researching Optics, I find that these Scouts don't receive the Embarkment promotion so they can't cross sea tiles. However, every Scout that I create after researching Optics has Embarkment.
My work-around thus far has been just deleting the Scouts I have out to be replaced by new Scouts. Is there something I'm doing wrong such that my Scouts aren't receiving the Embarkment promotion or is this "by design"?