The Windies lost 4-27 in eight overs of tight bowling with spinners Rachin Ravindra and Felix Murray stifling the Windies batsmen. On such a good batting wicket a total close to 300 was needed but the Windies stumbled through to 233-8 off their 50 overs.
Opener Simmons batted through the innings for 92 not out off 132 balls - no mean achievement - but his inability to lift the tempo of his innings cost him a deserved hundred and his team 30-40 runs.
Any nerves or doubts in the young Kiwis team when they began the run chase were soon put to rest by an outstanding display of top order batting.
Ravindra followed up his three wickets by helping Jakob Bhula put on 46 for the first wicket before he was out for 16. Out to the crease strolled Finn Allen and the young Aucklander began a match-winning innings that was full of aggressive sweeps, reverse sweeps and powerful drives down the ground.
Allen and Bhula began their partnership in the 10th over and batted with little discomfort and a great deal of youthful exuberance though to the 37th over with the score on 209.
To the surprise of everyone at the ground Bhula hit a soft catch back to spinner Alick Athanaze on 83 to end the partnership of 163. But the match was already as good as over and there was time to rejoice in Allen's 115 not out made off 100 balls, including 15 boundaries and two meaty sixes.
New Zealand have never won the ICC Under-19 Cricket World Cup since it began in 1988 but neither captain Boshier or Allen was getting too carried away after the win. They know that two years ago in Bangladesh the Windies lost their opening game but went on to clinch the title in a memorable final.
"I am pretty pleased how we went today but there are still a lot of things we can work on and want to improve, like fielding as a unit and the bowling early on," Boshier said.
"Credit to the Windies they put us under pressure early but I am proud of how we came back and started controlling the bowling innings."
Windies 233-8 (Keagan Simmons 92*, Kimami Melius 78, Alick Athanaze 26; Rachin Ravindra 3-30, Matthew Fisher 3-61, Felix Murray 2-37) lost to New Zealand 234-2 (Finn Allen 115*, Jakob Bhula 83) off 39.3 overs.
ICC Under-19 Cricket World Cup
Matches at Bay Oval, Mount Maunganui, 50 overs, 2pm starts. Free entry to all matches.
January 16 India v Papua New Guinea
January 17 West Indies v South Africa
January 19 India v Zimbabwe
January 20 New Zealand v South Africa
February 3 ICC Under 19 Cricket World Cup Final