The silky southpaw, ranked 34 by world governing body AIBA, danced and smiled his way through his semi-final bout at the ExCel arena, the 18-year-old toying with Ireland's Michael Conlan before recording a 20-10 victory which could have been more.
The Cuban opted to cover up in the first two minutes of the bout against the eager Conlan, who rained down blows which Carrazana fended off with his gloves before unleashing punches from all angles to leave the Irishman guessing.
Carrazana's performances across the week in London have been a highlight and he will start as favourite for gold on Sunday when he takes on Nyambayar and the expectation from back home as he tries to win Cuba's first boxing title since the 2004 Athens Games.
"We know the Olympics are the biggest show on earth when it comes to sporting events but when you're in the ring everything is the same, you could be anywhere," Carrazana said, attempting to play down the pressure.
The Cuban showman is likely to face a sterner test in the final against Nyambayar, who easily swatted aside Russian world champion Misha Aloian 15-11 in the first of 10 bouts in Friday's evening session.
The 20-year-old student proved too quick for a lethargic Aloian, the top seed, and routinely landed strong jabs and big right hands through the Russian's lazy defence.
Nyambayar is part of a quartet of Mongolian fighters that have impressed in London with their aggressive style, but the last one standing will aim for his country's first gold of the Games when he takes on Carrazana.
"The Mongolian people have a great history and I will be really proud to get a medal for Mongolia," he said.
"The population of Mongolia is not that big, it's only 2.8 million people and despite this, we are extremely proud of our history. It will be a great honour to get the medal."
While Carrazana aimed to please, his compatriot, Yasnier Toledo Lopez, opted for survival tactics but was beaten by classy Ukrainian Vasyl Lomachenko 14-11 in their lightweight semi-final.
The 24-year-old Beijing featherweight gold medallist has proved a class above in the heavier 60 kg category and after handing Lopez a small Ukrainian flag, his custom before bouts, he set apart picking holes in the Cuban's defence.
Fearful of Lomachenko's speed, Lopez kept his gloves high throughout the bout but the Ukrainian patiently punched holes to claim a narrow but deserved win.
"It was a really tough fight. But I must say he punched me a lot with his forearm, and I don't think that's good for the judges," Lopez bemoaned.