Viljoen top scored with a patient 42 to help his side post a modest total of 172.
He then carved through the Taieri batting line up to help dismiss the visitor for just 106 at Sunnyvale.
He was both frugal and deadly, taking four for nine from 10 overs. He also bowled six maidens to keep the squeeze on.
Veteran spinner Mark Joyce proved difficult to get away as well. He took three for 20 from the best part of eight overs, while left arm quick Blair Soper's return of two for 26 was a tidy effort, as well.
Jack Hunter top scored for Taieri with 25.
Green Island is undefeated after three games but struggled a little with the bat.
Openers Brad Wilson (14) and Gregor Croudis (20) and form batsman Tom Beaton (0) were dismissed within the space of five balls. Viljoen and Joyce (28) added 44 for the seventh wicket which was valuable in the context of the game.
Matt Bruce was the pick of the Taieri bowlers, with three for 27.
Kaikorai 330 for nine beat Albion 253
Rhys Bayly pummelled a career-high 180 to help Kaikorai beat Albion by 77 runs at Culling Park on Saturday.
The right-handed struck 18 fours and four sixes before he was caught on the boundary in the penultimate over.
It was a tremendous catch by Taylor Cumberland on the boundary which denied Bayly an opportunity to press for a double hundred.
There was also a touch of irony that he was dismissed in such acrobatic fashion, given it was by far the hardest of the four or five opportunities he offered during his wonderful innings.
Bayly actually fumbled his way through the early overs. He played and missed and French cut the ball.
But once he got in, the boundaries started flowing. He dispatched many delightful drives.
It was easily his highest score and one of the highest scores, if not the highest, posted in the tournament's history.
With help from Joshua Preston (53) and Ben Donkers (53), Bayly helped his side post a formidable total 330 for nine.
Jamie Glenn swatted 123 from 94 deliveries - his second club hundred this season - to give Albion a chance. But the target proved way too many.
The chase ended with Albion all out for 253 in the 43rd over.
Bayly was the star but Ryan Whelan played on with a dislocated finger and took three valuable wickets while chugging into the wind.
University-Grange 110 lost to NEV 111 for six
North East Valley secured an early finish at Ocean Grove with a four-wicket win against University-Grange.
University-Grange has returned to the grade after a four year absence and is battling but has recorded three consecutive losses.
Saturday's loss can be firmly tracked back to a poor start with the bat. It slumped to 12 for four and three of the top four batsmen failed to score.
Veteran seamer Jamie Murley (three for 23) and South African Travis Muller (four for 14) took seven wickets between.
University-Grange rallied to reach a modest 110 which was never going to be enough.
Muller's haul will not go unnoticed by the Otago camp. The 25-year-old has a very useful first-class record and turned out for Wellington last year.
He has moved further south in the hope of playing for the Volts and has made an impressive start.
Valley hurried through the chase, overhauling the target in the 23rd over. Tom Griffin top-scored with 32.
Josh Taylor was the best of the University-Grange bowlers with one for 33 from 10 overs.
