Explain the meaning of the quote:, "Scrooge had often heard it said that Marley had no bowels."

"Bowels" used in this sense at this period of time refers to compassion or pity. In general, bowels were considered to be the "tender feelings". This archaic meaning is no longer used for the word "bowels".  Therefore, Scrooge is referring to the comments made by others regarding Marley. He supposedly was not a generous man either. Perhaps Scrooge is justifying his own behavior.