It didn't take long for Isaac McHardie and William McKenzie to go from being in the hunt for medals at the Olympic test event to having a target on their backs.

The young 49er duo moved into the gold-medal position halfway through fleet racing in Marseille overnight but had to dig deep after an early setback.

A 20th place in the penultimate race threatened to derail their campaign, but McHardie and McKenzie fought back with a win to round out day four in the picturesque French city.

'It was another extremely tricky day and in the second race. We were deep in the trenches, and we couldn't really dig ourselves out, which was unfortunate,” says McHardie.

'It meant a pretty high score, but we managed to come together as a team and sort of figure the racetrack out and come into the next race guns blazing. We worked bloody hard to win that last one.”

McHardie and McKenzie have enjoyed a rich vein of form since claiming bronze at the Princess Sofia Regatta in Spain in April but with the Swiss and Croatian crews breathing down their necks in Marseille, there's plenty to do before any thoughts of another podium.

'Obviously, we're pretty happy with how the day went and we're stoked to be sitting on top but there's two more days of fleet racing, and it's all to play for,” says McHardie.

While they are the sole Kiwi crew atop the leaderboard, McHardie and McKenzie aren't the only ones firmly in medal contention.

Nacra 17 pair Micah Wilkinson and Erica Dawson have moved into third overall, following two top-three results bookending an 11th.

They are tied on 18 points with second-placed Paul Kohlhoff and Alica Stuhlemmer of Germany and are only six points behind Italian leaders Gianluigi Ugolini and Maria Giubilei.

'Today was another good day. It was really tricky so we're pretty happy to get two out of three good races,” says Dawson.

'It was very patchy on the water, so it was all about linking the pressure and I think we did an OK job of that.”

Wilkinson and Dawson are also pleased with the improvement they've shown since their 10th place at the World Cup in Hyères in May.

'Hyères exposed a bit of a weakness in the light air for us and it's something we've been working on a lot recently,” says Dawson.

'We're happy to see today that we have made gains in our light-wind technique.”

The fickle breeze was also top of mind for New Zealand's two windfoilers – with Veerle ten Have and Josh Armit managing only one race.

While Armit started his ascent up the men's leaderboard with a second place to take him to 14th overall, ten Have battled to just get on the foils.

'Today was definitely more floating than foiling. It was a long day of waiting, about five hours ashore, and when we were sent out it was pretty light - maybe five to seven knots,” says ten Have.

'Only about six girls got foiling off the start, and I got a DNF (did not finish) because I timed out in that race.

'It's all part of learning though and, luckily, we only had one race in that light stuff.”

Ten Have remains third overall, one point adrift of China's Xianting Huang in second.

Justina Kitchen is also on track for a spot in the medal series. She is ninth overall in the women's kitefoil after finishing with a fifth place last night.

Lukas Walton-Keim climbed one spot to 15th in the men's event.

Elsewhere, Jo Aleh and Molly Meech had a tough day in the 49er FX with scores of 12, 20 and 18 to sit 18th in the 49er FX standings.

Conditions are expected to improve tomorrow, in time for the return to action of George Gautrey (sixth) and Olivia Christie (24th) in the ILCA 7 and ILCA 6 competitions, following a rest day.

According to Yachting New Zealand's high performance director Ian Stewart, the test event is proving invaluable as preparation for next year's Olympic Games which will be sailed at the same venue.

'Racing conditions certainly have been testing but that's what we're here for. It does give us a decent look at what next year will provide,” says Stewart.

'It is also encouraging to see our sailors win a few races and put themselves in the hunt. Plenty of performance gaps have also been identified, but again, that makes it exciting and there is lots of room to move.”

Results and standings from day 4 of the Olympic test event in Marseille:

49er (29 boats)
1st: Isaac McHardie/William McKenzie (NZ) 14 4 3 5 20 1 - 27 points
2nd: Sebastien Schneiter/Arno De Planta (Sui) 6 2 5 14 4 10 - 27 pts
3rd: Sime Fantela/Mihovil Fantela (Cro) 1 3 15 8 13 5 - 30 pts

49er FX (23 boats)
1st: Odile Van Aanholt/Annette Duetz (Ned) 3 6 3 (22) 1 1 - 14 pts
2nd: Vilma Bobeck/Rebecca Netzler (Swe) 13 1 1 1 2 (14) - 18 pts
3rd: Stephanie Roble/Maggie Shea (USA) 1 5 (15) 7 3 2 - 18 pts
18th: Jo Aleh/Molly Meech (NZ) 11 (22) 7 12 20 18 - 68 pts

Nacra 17 (18 boats)
1st: Gianluigi Ugolini/Maria Giubilei (Ita) 2 7 8 1 1 1 - 12 pts
2nd: Paul Kohlhoff/Alica Stuhlemmer (Ger) 1 1 2 6 8 9 - 18 pts
3rd: Micah Wilkinson/Erica Dawson (NZ) 3 3 7 2 11 3 - 18 pts

ILCA 7 (42 boats)
1st: Michael Beckett (GBR) 2 5 2 4 (7) 1 - 14 pts
2nd: Jean Baptiste Bernaz (Fra) (11) 8 1 2 2 6 - 19 pts
3rd: Matt Wearn (Aus) 1 7 5 (10) 5 2 - 20 pts
6th: George Gautrey (NZ) (15) 9 12 3 1 4 - 29 pts

ILCA 6 (38 boats)
1st: Marit Bouwmeester (Ned) 2 2 11 (12) 2 7 - 24 pts
2nd: Maud Jayet (Sui) 6 4 4 (14) 5 5 - 24 pts
3rd: Chiara Benini Floriani (Ita) 1 9 (15) 5 10 2 - 27 pts
24th: Olivia Christie (NZ) (36) 30 8 18 23 20 - 99 pts

Men's windfoil (24 boards)
1st: Nicolo Renna (Ita) 1 1 9 4 (15) - 15 pts
2nd: Nicolas Goyard (Fra) 12 2 1 1 (21) - 16 pts
3rd: Noah Lyons (USA) (25BFD) 5 4 3 8 - 20 pts
14th: Josh Armit (NZ) 8 19 (21) 17 2 - 46 pts

Women's windfoil (23 boards)
1st: Emma Wilson (GBR) 3 1 1 1 (8) - 6 pts
2nd: Xianting Huang (Chn) (24DSQ) 8 2 4 1 - 15 pts
3rd: Veerle ten Have (NZ) 6 3 5 2 (24DNF) - 16 pts

Men's kitefoil (20 boards)
1st: Axel Mazella (Fra) 1 (5) 2.2RDG 1 2 2 1 2 2 (3) (3) - 13.2 pts
2nd: Connor Bainbridge (GBR) 2 (4) 3 (16) 4 3 4 3 1 1 (12) - 21 pts
3rd: Maximilian Maeder (SGP) (14) 1 (16) 3 3 5 2 1 10 (21DNF) 2 - 27 pts
15th: Lukas Walton-Keim (NZ) (17) 14 13 13 (17) 14 14 11 14 6 (17) - 99 pts

Women's kitefoil (20 boards)
1st: Lauriane Nolot (Fra) 2 1 (7) 1 1 (4) 1 1 3 1 (7) - 11 pts
2nd: Eleanor Aldridge (GBR) 1 2 (11) 2 4 (9) 3 (6) 1 2 1 - 16 pts
3rd: Daniela Moroz (USA) (12) 5 3 3 2 1 (9) 2 4 3 (9) - 23 pts
9th: Justina Kitchen (NZ) 6 9 (15) 10 8 7 10 11 (21DNF) (12) 5 - 66 pts