Does this poem flow? Or did I make it too choppy?

I don't like the title. I would recommend "A Midshipman's Dream" or the like. Your meter is off in places. I'd also eliminate the two lines beginning with "Send those demons...." They come off as a bit corny. If you want to keep the same idea maybe try something like "Send the s to the Devil, Fire when the guns are level." That would also tie it together with the following lines about loading and firing the cannons. Best of luck!