Overcoming three picks, the 6-foot-3, 200-pounder hit on 19 of 32 passes for 224 yards and three touchdowns and gained team MVP honors. Midway through the fourth quarter, he capped the spirited comeback with a 25-yard scoring run.
For his career, Mornhinweg, who has committed to play at Penn State, threw for more than 4,800 yards and 52 TDs. He also rushed for 1,200 yards and 17 scores.
"What more can you say about the young man?" Hawks coach Gabe Infante said. "He went through a lot over the last four years, but he battled all the way. He deserves so much more, but at least he finished with a win."
After a 4-7 campaign last season, including a 14-13 loss to Malvern, the Hawks posted a 7-4 mark. They trimmed the Friars' series advantage to 3-2.
"That was a big and physical team we played," Hawks senior wideout Jim Hurley said. "They got off to a good start, but I don't think we ever doubted ourselves. It was about playing better as a team."
In the second quarter, after Tim Rafter's fumble recovery, St. Joe's trimmed the deficit in half on Mornhinweg's 26-yard pass to tailback Vince Moffett.
The first of Mornhinweg's two TD tosses to Hurley, a 33-yard connection on a post route, and a missed extra-point boot made it 14-13 at the break.
Hurley, slowed much of the season by a high ankle sprain, totaled 108 yards on eight catches.
"He finally got healthy," Infante said. "Obviously, the 18-day layoff we had was good for him."
Hurley's 5-yard TD grab, on a left-to-right slant, and Eric Medes' two-point conversion run gave the Hawks a 21-14 lead with 3 minutes, 5 seconds left in the third quarter.
In the fourth quarter, Todd Jones surged into the end zone and corralled Malvern quarterback Billy Ford, who took over for starter Tommy Rumer (knee injury) in Week 9, to make it 23-14.
The sixth-ranked Friars (9-2) had jumped in front, 14-0, on fullback Joe Nilan's 39-yard rumble around the right corner and Joe Carlini's 39-yard interception return. Carlini added two more INTs to earn team MVP honors.
Malvern Prep 7 7 0 0 – 14
St. Joseph's Prep 0 13 8 9 – 30
MP: Nilan 39 run (Gabert kick)
MP: Carlini 39 interception return (Gabert kick)
SJP: Moffett 26 pass from Mornhinweg (Battin kick)
SJP: Hurley 33 pass from Mornhinweg (kick failed)
SJP: Hurley 5 pass from Mornhinweg (Medes run)
SJP: Safety
SJP: Mornhinweg 25 run (Battin kick)
Contact staff writer Rick O'Brien at 610-313-8019, robrien@phillynews.com, or @ozoneinq on Twitter. Read his blog, "The O'Zone," at www.philly.com/ozone