Rick Porcello (1-0) allowed a run and three hits in 6 2-3 innings in his first start of the season, and the Tigers (4-0) remained baseball's only undefeated team. But the Orioles nearly pulled off a remarkable rally after trailing 7-1 entering the ninth.
Hunter hit a three-run double in the third, then added a two-run drive in the fifth for his second homer of the year.
Bud Norris (0-1) allowed five runs and nine hits in five innings, and the Orioles lost their fourth straight.
Detroit's Brad Ausmus became the first manager in more than a decade to begin his career with four straight wins, according to STATS. Clint Hurdle of Colorado and Jerry Royster of Milwaukee both did it in 2002.
Ausmus took over for Jim Leyland after last season, and the three-time defending AL Central champions are off to a good start - although the Tigers nearly frittered this game away.
Steve Lombardozzi singled to deep right to load the bases, and pinch-hitter Steve Clevenger's double made it 7-5. David Lough brought home another run with a grounder to shortstop Alex Gonzalez, who threw wide of first for an error.
With men on first and second, Nathan struck out Nelson Cruz and got Davis to hit a lazy fly to left.
The 25-year-old Porcello already has five full seasons under his belt. If he blossoms into a true standout, Detroit's already-excellent rotation will look even tougher.
Porcello struck out only three with two walks, but he didn't allow a hit after the second inning. Only one of the final 17 batters he faced reached base.
Davis opened the scoring in the first with an RBI single for Baltimore, but he was thrown out trying to take second. The Tigers took the lead in the third when Hunter's line drive to the corner in left field cleared the bases. His homer in the fifth made it 5-1.
The Tigers have hit six homers in their first four games, an encouraging sign after they traded cleanup hitter Prince Fielder in the offseason. Kelly had three hits Saturday, while Hunter, Davis, Ian Kinsler and Austin Jackson added two apiece.
The bottom three hitters for Detroit - Gonzalez, Kelly and Davis - combined to go 6 for 10 with two RBIs and five runs scored.
NOTES: The temperature at game time was 41 degrees. ... Orioles SS J.J. Hardy prevented further damage in the third with a diving stop on Victor Martinez's grounder. ... Detroit's Justin Verlander (0-0) will face Baltimore's Chris Tillman (0-0) on Sunday.