You may well be right, but whoever created the transcription of the poem that ended up at OSU (Ohio State University, I think) will have to take responsibility for "coast." That collection of Howard material appears to have been part of the Bill Blackbeard collection. Glenn Lord sent Blackbeard copies of then-unpublished Howard verse, back in 1964.
Here's a little poser: In the first stanza of "Drake Sings of Yesterday," why does the final word not rhyme? And what synonym for the word that is used might? (I'll give you the fun of figuring it out on your own before I tell you.)
On Devon downs I met the ghost of Drake;
His sigh was a sea-wind that whispered past:
“Dost know barnacles crust the rotting strake,
And salt weed shrines the fallen mizzen-mast?
The sword of glory long has turned to rust. . .
Aye, shattered now the prows that long of yore
Beat up the sunset through the blinding gust
That lashed us off the gold-fat Carib coast.
The word "shore" retains the meaning, and rhymes. So why wasn't it used? Seems like some sort of editing error or other such glitch to me. Anyone (perhaps with access to manuscripts) have any further info?