I understand that ἀπ-αυράω can take a double accusative, and at first seems to here, since σε is accusative and so is νῆα μέλαιναν. What I don’t understand is how ἀέκοντος can be genitive, since it obviously refers to the same person (Noemon) as σε. It’s as though ἀπ-αυράω is taking the double accusative AND acc.-of-thing-bereft-of and gen.-of-person-bereft at the same time! What’s with that? Is it just to fit the meter?
Treating it as a genitive absolute with concessive force and ellipsis of ὄντος seems to work: “he took it from you by strength, though you were unwilling”
It is certainly awkward. But there’s a similar verse in the Iliad: 1.430 την ρα βιῃ αεκοντος απηυρων, “they took her away by force against his will” (re Briseis being taken from Achilles)—again αεκοντος gen. not αεκοντα acc. (which would indeed strain the meter, as you imply, though perhaps not quite intolerably at caesura). There we could take αεκοντος as a genitive absolute, “they took her away by force, (he) being unwilling.” That’s less easy here in Od.4, given the presence of σε, but obviously something similar is going on, and there’s formulaic pressure to consider. I think it’s significant that in both verses the phrase used is βιῃ αεκοντος, and βιᾳ/ῃ + genitive means “in spite of (someone)”, “against (someone’s) will” (LSJ βία II.2).
PS Now I see Merry’s note linked by Manuel, but I’ll let this stand regardless.