I'm afraid that the 'port out, starboard home' explanation is nothing more than an urban legend...and, as such, it supposedly referred to the journey to India, not America. The very first time the word appeared in print, meaning 'grand/swell' was in 1918, having earlier appeared as 'push' - with a "u" - in a P G Wodehouse story in 1903. As British officials and soldiers with wives and families had been sailing to and fro India for three centuries by then, it's clearly too late for that explanation to have any substance. It was also rejected in the 'Mariners' Mirror' decades ago and presumably sailors of all people would have known. According to the Oxford English Dictionary, it is probably no more than a corruption of Wodehouse's 'push'. Sorry to rain on the parade here, but the OED simply IS the "bible" of English etymology and it says the legend "lacks foundation".