Koa Maikuku then scored a long range effort just before the break after Moerewa standoff Wilsom Hona identified uncovered ground and kicked into space to give Moerewa a 10-8 lead.
Otangarei scored three tries early in the second half but were left to rue more missed conversions as Moerewa came back late with two tries of their own. Both were converted.
Otangarei coach Des Norstraund said it was a grinding effort from his side.
"We did well coming back from two weeks off," he said. "Only having 13 players, it meant the boys had to play tough."
Moerewa coach Peter Prime was content with the effort, but rued poor preparation and execution.
In other results, Northern Wairoa Bulls had a convincing 36-12 win over Hora Hora Broncos, while Takahiwai took a 38-22 home victory over Portland Panthers.