Porter pumped in 21 points and Starks added 16 for the Hoyas (18-4, 8-3 Big East), who caught up with the Golden Eagles for second place in the conference with their sixth straight win.
Both teams remained 1/2-game in back of Big East leader Syracuse.
Nate Lubick also reached double figures for Georgetown with 10 points.
Marquette (17-6, 8-3) turned the ball over 19 times and got a total of nine points out of leading scorers Vander Blue and Davante Gardner in the setback.
Jamil Wilson netted 13 points and Chris Otule added 11 for the Golden Eagles.
2014: The Year in Music [PHOTOS]