Asian Games silver-medallist Manpreet clinched a comprehensive victory over Seychelles' Keddy Agnes, while sixth seed and Commonwealth Games champion Manoj got the better of 2011 European champion Fatih Keles of Turkey.
Both Manoj and Manpreet had got first-round byes.
Manpreet won 3-0 in the overall analysis with the round-by-round break-up being 30-27 30-27 30-27. Manoj, on the other hand, fought through a see-saw battle even though he too emerged 3-0 victorious at the end of the bout.
Manpreet, a silver medallist at the 2010 Asian Games, has had a long break from competition and is playing his first international tournament this year.
Friday, he was seen in full flow against the Seychelles boxer. His hard hitting uppercuts and jabs did a lot of damage and put Keddy on the back foot right from the very beginning. Manpreet went on to make the pre-quarters by virtue of a unanimous decision.
"Manpreet dominated all three rounds even though the other guy was very stout and experienced. Manpreet put to use some precise uppercuts and straight punches to unsettle him," national coach Gurbax Singh Sandhu said.
"It was a fine performance and Manpreet did not give any chance to the other guy," he added.
The 28-year-old will now face world number one and Olympic bronze-medallist Teymur Mammadov of Azerbaijan, who has been top-seeded, in the round of 16 on Monday.
Mammadov, the current European Championships silver-medallist, got a first-round bye and he thrashed Efetobor Apochi of Nigeria in his opening bout on Friday, which preceded Manpreet's bout.
"No doubt it is a tough bout but let us see. We will plan and work out our strategy. We have seen this boy and he is a top boxer but Manpreet is no less," said Sandhu.
The 20-year-old Mammadov had won a silver medal in the 2011 World Championships in Azerbaijan besides being the European champion in that year.
Manoj, meanwhile, will be taking on Canada's Yves Ulysse, who defeated Juan Romero of Mexico. The Manoj-Ulysse clash is also scheduled for Monday. "Manoj fought from long range in the opening round and in the second round, the other guy resorted to some tempo boxing. It was an intense bout but Manoj dominated the final round," said Sandhu.