Fresh from beating the number two seed earlier, Fares traded point for point in the opening game. Mahesh was taking the ball early and at 10-all won two sweet points to win the first game 12-10.
In the second, Fares came out strong and Mahesh was forced into making a few errors due to the attack of the Egyptian teenager who also showed a magnificent arsenal of shots to keep the crowd at the edges of their seats.
The fourth game always had one winner and Mahesh was literally the last man standing on the day. The 14-12 9-11 11-8 11-1 victory after 77 minutes takes world No.88 Mahesh through to meet fourth seed Mazen Hesham Ga Sabry.
The world No.45 from Cairo, also 19, removed Indian No.2 Harinder Pal Sandhu 12-10 11-9 11-8.
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The other semi-final will be an all-Egyptian affair between unseeded Zahed Mohamed and third seed Ali Anwar Reda. Reda, who upset top seed Ong Beng Hee in the first round, beat Indian hope Ravi Dixit 11-8 11-5 11-5.
Results: Quarter-finals
Zahed Mohamed (EGY) bt Ravi Dixit (IND) 11-8 11-5 11-5 Ali Anwar Reda (EGY) bt Johan Bouquet (FRA) 7-11 11-7 11-6 11-1.
Mazen Hesham Ga Sabry (EGY) bt Harinder Pal Sandhu (IND) 12-10 11-9 11-8.
Mahesh Mangaonkar (IND) bt Fares Mohamed Dessouki (EGY) 14-12 9-11 11-8 11-1.