ὅτι introduces oratio obliqua with verbs of perception,
We have a counterexample in ἤκουε in this very passage. Verbs of perception generally take accusative + participle, but can also take ὅτι if they indicate “intellectual perception” (Smyth’s term). Here ᾔσθετο here is followed by ὅτι, but ἤκουε is followed by Τάμων ἔχοντα, participle + accusative.
Loeb has it right.
I think you’re missing the point.
The Loeb translation doesn’t follow the syntax of Xenophon. Ταμὼν ἔχοντα, not τριήρεις … περιπλεούσας, must be the object of ἤκουε. Otherwise Ταμὼν ἔχοντα would have no function in the sentence. τριήρεις … περιπλεούσας has to be the object of ἔχοντα, not of ἤκουε.
“he was hearing that Tamos had command of triremes . . . sailing around from Ionia to Cilicia.”
not
“he was hearing that triremes were sailing . . . under the command of Tamos”.
The Loeb translation is ok, however, even if not literal.
Maybe there is a kind of free-standing accusative of military command without preposition (like the so-called “dative of military accompaniment”) but I’m not aware of it and couldn’t find any such construction in Smyth.
I think Xenophon was writing hastily. The natural tendency of a reader, I think, would be to take τριήρεις as the object of ἤκουε. Perhaps that was how X. started out writing the sentence, but then he had second thoughts, adding Ταμὼν ἔχοντα and changing the syntax of the sentence.
Ταμὼ ἔχοντος (genitive absolute), a conjecture reported by Marchant (attributed to Gemoll–does this mean g minor?–or to an earlier conjecture cited by Gemoll), would make τριήρεις the object of ἤκουε. A plausible (I think) explanation for a change from genitive to accusative: Step 1–the unusual name with its Attic declension led a copyist to think that the genitive was accusative (like Σαπφω), and to change ἔχοντος to ἔχοντα; Step 2–another scribe further downstream, recognizing the Attic declension, changed genitive Ταμὼ to Ταμὼν to agree with ἔχοντα.
This conjecture, I think, would make the text read more smoothly, which of course is an argument against it, particularly since it isn’t impossible to make sense of the accusative reading of the mss. The errors would also have to have occurred at a relatively early point in the history of the text–probably in antiquity–since the accusative is apparently found in all of the mss., as far as I can determine. That’s another strike against the conjecture, but it does show that someone besides me had difficulty with the text as it stands.