Explanation: A visceral feeling is something you feel in your gut that differs with what your first initial thought is. The best way I know to explain this is with food.
You see the salad and your brain says to eat that, but your visceral gut says to eat the cake.
These battling emotions cause you to not be able to make a decision
In this passage, Douglass does say he knows he left on a Saturday but did not know what day of the month or the year it was. He also knew terms of a ship because he used them the passage.