The win gives Otago a maximum of four points and 15 games and it leads section two by half a point from Northland, with daylight back to third.
Otago meets Northland this morning and Wellington this afternoon. A win in the morning match will ensure the team qualifies for the semifinals in top slot.
Waikato is leading section one with four wins after beating North Harbour 4.5-0.5 yesterday, and, if all goes to plan, it could be a repeat of the 2014 Otago-Waikato final tomorrow afternoon.
On the eve of playing his 100th national interprovincial game for Otago, No3 Brent McEwan was in good form yesterday despite atrocious conditions.
McEwan halved the first three holes with Hawkes Bay's Brad Truesdale but birdied the fourth and parred the fifth to open up a lead of two.
He lost a ball on the sixth hole but retaliated, winning the next two holes to turn 3up.
McEwan won the next three holes to increase his lead to six, and, when the pair halved the 13th, the match was finished.
No4 Fraser MacLachlan followed on from his resounding 5 and 4 win on Wednesday afternoon, opening up a big lead of six by the turn.
MacLachlan won holes 1, 2, 4, 5, 6, 7 and 9, losing the third to a par while the pair halved the eighth hole in pars.
On the back nine, MacLachlan won the 11th but lost the 12th, finishing the match with a 6 and 5 margin on the 13th green.
Otago No2 Nick Borren was also back to his best after an atypical front nine on Wednesday afternoon, going down on the penultimate green.
He won the first five holes with four pars and a birdie 4 on the second hole but the margin was reduced to four when he lost his ball at the sixth.
His opponent, Dallas Williams, birdied the next hole to get back to three behind and the next three holes were all halved.
Borren went 5up when Williams bogeyed the 11th and 12th holes but he showed better form to birdie the next hole.
Borren was keen to escape from the drenching weather and he finished the match with an impressive birdie 3 on the 14th hole.
Otago No 5 Chris Snow found himself in unfamiliar territory, holding a good lead through his round, turning three ahead of Ben Swinburne.
He lost the 11th to a birdie, going into the final four holes two ahead, in sharp contrast to Wednesday's situation when he came from behind twice to post two valuable wins.
He went three ahead with a birdie on the 15th and the match finished one hole later when Snow and Swinburne halved the hole with pars.
Otago No 1 Duncan Croudis went into yesterday's contest unbeaten but met a determined Russell Mitchell, who relished the wet conditions.
The lead oscillated on the front nine but Croudis lost the ninth to a birdie 3 to go on to the back nine to trail by one.
Consistent par golf by Mitchell on the back nine made it hard for Croudis to make inroads and he went two behind when he came up short on the 14th hole.
Croudis ran out of holes when the pair halved the next three holes and the match finished with a Hawkes Bay win on the 17th green.
The Waikato team is dominating section one but No5 Chris Charlton made his own statement when he sank an 8 iron for a hole in one on the 141m par-3 12th.
