Five NZ boats enter the A finals at the World Rowing Champs

New Zealand booked four more crews into finals at the rowing world championships in Florida but an apparent weakness in mid-sized boats has been exposed again.

France's unbeaten world and Olympic champions in the lightweight men's double sculls, Pierre Houin and Jeremie Azou, won easily ahead of Poland's Jerzy Kowalski and Milosz Jankowski and Lucas Schaefer and Jason Osbourne of Germany.

In the women's lightweight double, Kat Copeland and Emily Craig also secured a final place, taking the third spot in a semi-final where just 1.8 seconds separated the top three.

That session is also when the four remaining Kiwi boats to book finals berths.

James Hunter and Thomas Murray had to settle for second behind the Italians in their semi.

The New Zealand team in Florida features a host of new crew combinations and single scullers from the group that contested last year's Rio Olympics, but a string of World Cup medals in Europe and further strong showings this week has indicated the sport is in good shape as it already eyes the 2020 Tokyo Olympics.

Ireland's defending world champion in the lightweight men's single sculls, Paul O'Donovan, timed his effort perfectly to win his semi-final, taking over the lead from Switzerland's European champion Michael Schmid in the third 500 metres, with Brazil's Uncas Batista taking the third qualifying spot after overtaking the World Cup III victor, Artur Mikolajczewski of Poland.

Weronika Deresz and Joanna Dorociak of Poland took second and Denmark's Aja Runge Holmegaard and Juliane Rasmussen third.

The men's quadruple sculls will contest Saturday's B final.

South Africa's Olympian Kirsten McCann, who has already won a World Cup medal after switching from the double to single in the lightweight women's sculls this season, was a dominant victor of her semi-final, ahead of Switzerland's Particia Merz and Marieke Keijser of The Netherlands.

Dunham will chase his first world rowing championship medal after finishing second in the second semifinal.

Britain now has 12 boats in A finals after six crews advanced on Wednesday. Norway's Kristoffer Brun came through to take first place, with New Zealand's Matthew Dunham second and the fast-finishing Lars Wichert of Germany qualifying in third. Croatia, Great Britain and France qualified from the second semi.

The Kiwi men's eight of James Lassche, Drikus Conradie, Patrick McInnes, Isaac Grainger, Shaun Kirkham, Michael Brake, Brook Robertson, Stephen Jones and coxswain Caleb Shepherd sealed their spot in the blue riband final when second in their repechage. Australia, Denmark and Germany progressed to the A final.

Earlier this week, the NZ women's eight qualified directly for the A final by winning their heat in an upset over the host crew.

A formidable Lithuanian boat took first with Estonia and Norway rounding out the top three.

Lightweight single sculler Matt Dunham, the men's pair, lightweight women's double sculls and the men's eight all progressed to the A final while the men's four and men's quad will contest the B final.