Penijamini Nabainivalu scored two tries, while his fellow Islanders Iliesa Ravudra and Isei Lawaqai got the others.
They stayed ahead of the team they defeated the previous weekend, South Canterbury, who held on for a crucial 32-28 win over Poverty Bay in the Top 4 clash in Timaru.
Tenari Saumani scored a double for the home side, while Poverty Bay still picked up two bonus points by scoring four tries, which keeps them clear of Thames Valley in fifth spot.
Horowhenua Kapiti moved up to third as they continue their strong season by just holding off a desperate Wairarapa Bush 12-9 in Levin.
No tries were scored with Perry Hayman's four successful penalties being enough against Grey Mullany's three.