With the potential for rain and a wet surface at Harry Barker Reserve, games were held on Nelson Park's artificial-turf wickets.
The change in venue favoured the spin bowlers, who got good turn and bounce.
OBR were on track with their run-rate going into drinks midway through their innings, but were eventually dismissed in 31.2 overs.
Horouta's win came on the back of a good batting performance by the team's top order, after they lost the toss and were sent in to bat by OBR.
The first four batsmen scored at least 25 runs as they stormed to 208-7 in their 40 overs.
Kulaar's heroics weren't confined to bowling, as he made 49 runs opening the batting for Horouta.
With captain David Situ scoring 27 off 30 balls, Horouta were already off to their best start of the season.
Situ said that while Kulaar was deservedly player of the day, he was more impressed by the way everyone supported the bowler.
“We talked about how all we needed really was for someone to step up.
“He and I were getting five or six (runs) an over before I got out, then Tushar (Balat) came in and kept the run rate going.”
Handy contributions of 39 from Keegan Martin and 37 from Balat put Horouta in a commanding position as they entered the final stages of their innings.
With 15 overs remaining, Horouta looked as if they could push for 250, but their momentum stalled late, and they were unable to capitalise on their blistering start.
OBR had chances to take key wickets early but weren't able to make the important, but difficult, catches stick.
The field had much shorter boundaries than those at Harry Barker Reserve, and it was uncertain whether the Horouta total would be enough in a game where 37 fours and six sixes were scored.
The game was in the balance for the majority of the OBR innings. Momentum swung back and forth as the teams traded blows.
OBR had a blistering start to their innings through opening batsman Greeks, who hit 65 runs off 57 balls. He smashed 12 boundaries, two of them sixes, in a display of power batting.
But with his dismissal, OBR lost their composure and collapsed, captain Ian Loffler said.
“We knew if we batted our 40 overs we'd win, and that's how we went about it at the start before a good bowling spell by Parry (Kulaar) with the leg-spin.
“We had the game in the bag and we sort of fell apart and gave our wickets away.”
Loffler said it was a good game of cricket as both sides tussled for control.
Horouta's hunger for their first win was palpable, and the feeling intensified with the fall of each wicket.
The final wicket brought relief and joy as the team celebrated a hard-fought win.
Situ said the game was in the balance after a poor bowling performance in the first half of the OBR innings.
“Our bowling in the first 15 overs definitely wasn't what we were looking for, but as soon as the innings started crumbling, the team's energy lifted.
“It was a big team effort. Everyone played well and did their part. It's what you want towards the back end of the competition.”