The Gurias registered first points from a penalty in the opening minutes from boot of Elipas Pidik.
Pidik made it 4-0 not long after Isapea gave away another penalty right in front of the posts.
But it was the Gulf boys who crossed the tryline first when five-eighth Solomon Pokari Kale slipped a no-look pass to Jack Manda who ran in to score.
Japheth Olik put his side in front after converting the try.
But the Gurias hit back straight after with quick hands that created an overlap for Pidik to score out wide.