Hopefully it should be enough, given this ship is likely smaller than a Greek warship/trireme. Apparently those, fully decked out and carrying ~200 men, would weigh about 50 tonnes, which is double the pegasus's max push. However, this small merchant ship, with far fewer sailors/oarsmen, is likely less than half the size, right? So it should work out pretty well.
For reference, that pegasus right now could carry more than 10 of my character and hardly even notice.