Fiona Murtagh overcame a less-than-perfect start to match the win in her heat and take a place in the semi-finals.
There was a late lift for Ireland as Konan Pazzaia produced an outstanding performance to take second in his heat of the single sculls and qualify directly for the quarter-finals.
The pressure on McCarthy and Doyle was that they perform. McCarthy is a double Olympic gold medallist, but in a lightweight double. Doyle took bronze in the double in Paris, but with a different partner, Daire Lynch.
The best praise that could be lavished on them was that the new crew looked like a unit: they started well and led through all four quarters. Italy, with two former lightweights in Gabriel Soares and Niels Torre, took second and booked their place in the A Final.
Wednesday’s semi-final will be a much tougher test for Ireland: all the other heats were won in much better times. McCarthy and Doyle take on Olympic champions Romania, the fastest of all the heat winners, in the first semi-final (4.11 am Irish time).
Murtagh always looked likely to be the top gun in her heat and so it proved. However, she was slow to get going at the start.
Esther Zamorano of Spain led out the Irish woman, and it took Murtagh 1200 metres before she reeled the Spaniard in. From there, Murtagh sculled away serenely and won by 5.74 seconds.
Murtagh and her chief rival, Britain’s Lauren Henry, have avoided each other in the semi-finals. The Irish woman will compete at 5.42 on Friday, with her biggest threat in this race likely to be Viktorija Senkute of Lithuania, who won her heat.
Pazzaia is a doughty performer. The man who grew up in Switzerland with an Irish mother and now studies at Queen’s in Belfast, partnered McCarthy to two silver medals this year, only to be picked in the single, often the most difficult boat.
The top two were guaranteed only a quarter-final place, such is the size of the field – 30 crews. Pazzaia got a good start, but he was third at half way.
From there he covered the course faster than anyone and came within a third of a second of catching the winner, Bruno Cetraro Berriolo of Uruguay. He has a reasonable chance in his quarter-final (3.40 Wednesday), with the top three going to the semi-finals.
The new progression system, with no repechages, is a tough one and the Ireland women’s double and four did not make it through on the day.
Zoe Hyde and Mags Cremen fell the wrong side of the line in their heat of the double. With 12 crews competing, just the top two in each heat were guaranteed an A Final place, and only the next fastest two from both heats joined them.
China and the Netherlands were best in the Irish heat. The Individual Neutral Athletes, who were third, qualified on time, but Ireland’s fourth place did not get them through.
The picture was similar for the Ireland women’s four. This new unit raced well, but fourth in their heat was not enough to make the A Final.
The quality of the race was outstanding: New Zealand won from the Netherlands, with Australia third – and not making the A Final.