The Peacocks (11-9, 6-3 Metro Atlantic Athletic Conference) made only nine field goals inside the 3-point line, but finished 9 of 18 from 3-point range and clamped down on defense to preserve the victory.
Darius Conley added 12 points for St. Peter's, which shot 29.2 percent in the opening half (7 of 24) and trailed 26-25 at the break.
Manhattan (3-17, 1-8) outscored the Peacocks in the paint 26-12, but was held to 20-of-63 shooting from the floor (31.7 percent), including 2 of 11 from beyond the arc (18.2 percent).
George Beamon scored 12 points and was the only player in double figures for the Jaspers, who have lost 17 of their last 18 games after starting the season 2-0.
The Peacocks outrebounded Manhattan 48-36.
Oklahoma State basketball player Tyrek Coger died after a 40-minute team workout on the football stadium stairs in hot weather, university officials said Friday.
Prospective NCAA championship host cities must identify local anti-discrimination laws in a questionnaire being sent out by the college sports governing body.
The Class of 2017 is full of talented big men, but Richards is getting noticed by more programs during the current evaluation period in Las Vegas.