A place in the final beckons for either OBM or YMP when they play each other this week.
YMP are second on the points table but they lost 25-19 to Larsawn Ngatapa at Patutahi on Saturday.
OBM have not lost since YMP beat them in Round 1.
OBM coach Trevor Crosby said club members were “very happy” with where they were.
They have built depth in their squad, they’re fit and still look capable of raising their game to another level.
“We know everyone will be targeting us,” Crosby said.
Left wing Keelan Poi opened the scoring against Waikohu with a try for OBM after five minutes.
Hooker Rikki Terekia then scored an extraordinary try for OBM, taking advantage of a lot of space on the left and putting his team ahead 10-0.
Waikohu hit back with a try to flanker James Rutene.
But OBM second five-eighth Mark Atkins was breaching the defence almost at will and he dotted down twice.
Though Waikohu prop Sandy Hohipa-Campbell, who made several strong carries, crashed over for a try, OBM right wing Jale Tiko and halfback Willy Grogan both scored before halftime.
OBM led 36-12 at the break and the game was as good as gone.
Waikohu sometimes looked likely with ball in hand but OBM made them pay for errors.
No.8 Gabe Te Kani showed his strength to score a try, first five-eighth Jake Holmes crossed the chalk and Grogan went in for his second try.
Waikohu No.8 Toru Noanoa got one back but OBM lock Juston Allen then scored a popular try, latching on to an intercept and sprinting for the goal-posts.
Jesse Pikia got a consolation try for Waikohu.
Waikohu coach Jason Tuapawa was happy to come out of the game with key men such as inside backs Kelvin Smith and Mario Counsell still healthy.
“We’ll be ready to go (for the next game),” he said.
Ngatapa finished their season strongly, accounting for YMP after putting away HSOB the previous week.
Ngatapa coach Steve Hickey said YMP scored straight from the kick-off and his side also conceded a couple of “soft, long-range tries”.
But they hung in there.
“We just completely controlled the second half,” Hickey said.
Jason Jones played his 150th game for Ngatapa.
Loose forward James Maher provided leadership in the last two games, Hickey said, and Matt Raleigh and Lyle Crudis ran the backline well.
YMP coach Steve Smith said his team got a workout on defence in the second half, particularly in the forwards.
Whaimotu Craft-Chemis scored three tries for YMP.
Loose forward Jesse Kapene, who has been out since mid-May with a serious injury, made his return to action in the second half.
Smith said Kapene came through it OK.
The game was a chance to see who could step up for semifinals rugby, Smith said. He had some decisions to make about who to pick for this week.
HSOB centre James Warren said his team had a solid first half against Pirates-GMC, scoring three tries to one.
The sides were evenly matched in the second half.
“It was good to get a win going into the semifinals,” he said.
Warren said HSOB wing Tevita Lataipangai, lock Fletcher Scammell and No.8 Tamanui Hill were lively.
Will Bolingford, the Pirates-GMC player of the year, scored two tries in another powerhouse performance at flanker.
Pirates-GMC captain Ken Houkamau said his team were slow out of the blocks and then clawed their way into the contest.
Player-coach Willie Waitoa said that in their more recent performances the team showed they had grit.
