Williamson referred to Boult reaching 145-146kmph in last Sunday's T20 international at Mount Maunganui as the quickest he's seen from him.
"That's really promising because we know when he's bowling fast and swinging it for a long time he's been one of the best bowlers in the world.
"It's a good sign that he's getting rhythm. For a couple of years Trent and Tim were at the top of their game and they've still been bowling really well, even if it hasn't been the best they've wanted. They're certainly getting back to that point."
Unless the rain intervenes to a significant degree, expect New Zealand to win both tests against Bangladesh.
This is Bangladesh's weakest form of the game, especially away from home, and notwithstanding having won their most recent test, against England.
The Basin Reserve pitch was its standard healthy shade of green yesterday and while that should fade a touch by today, the seamers will get a decent crack through most of the first day.
If Bangladesh's seamers are searching for inspiration, look no further than their bowling coach, Courtney Walsh.
The former West Indies quick knows the Basin well. In 1995, he took the barely believable figures of 13 for 55 as New Zealand were poleaxed by an innings and 332 runs, the sixth worst test defeat in history.
Test captain and experienced wicketkeeper Mushfiqur Rahim has confidence in his bowlers to do a job.
"When you know as a group that you can take 20 wickets, it gives a bit of satisfaction," he said. "But we are playing in different conditions and we haven't played an away test in a very long time."
Bangladesh's talented 19-year-old offspinner Mehedi Hasan took 19 wickets in his first two tests against England last October, but how effective he'll be on the Wellington green was last night being debated by the tour bigwigs.
He should play, there's another puzzle too. The tourists have left comfortably their best seamer out of the test squad, left armer Mustafizur Rahman, ostensibly because he is returning from a long injury layoff although he played four of the six limited-overs internationals here. A shame, as he is a classy operator.
"They've got some really talented seamers," Williamson said. "They've got a lot of talent, but are slightly inexperienced in our conditions. Their experiences around the world will make them better players."
New Zealand v Bangladesh
First test, Basin Reserve, starts 11am Thursday
New Zealand: (probable) Kane Williamson ©, Jeet Raval, Tom Latham, Ross Taylor, Henry Nicholls, Colin de Grandhomme, Mitchell Santner, BJ Watling, Tim Southee, Neil Wagner, Trent Boult.
Bangladesh: (probable) Tamim Iqbal, Imrul Kayes, Mominul Haque, Manmudullah, Shakib al Hasan, Mushfiqur Rahim, Sabbir Rahman, Mehedi Hasan or Soumya Sarkar, Rubel Hossain, Taskin Ahmed, Kamrul Islam.
