The 52-year-old Plumtree, who was Ireland's forwards coach before he joined the Hurricanes ahead of the 2015 Super Rugby season, had been expected to take the top role after Boyd said earlier this year he was joining the English Premiership side.
Jason Holland, who is also an assistant coach for the Hurricanes, has been confirmed as Plumtree's assistant. Both have signed contracts through until the end of the 2021 season.
"We're fortunate that someone of Plum's calibre has already been a key part of the Hurricanes environment," Hurricanes chief executive Avan Lee said in a statement on Wednesday.
"Having both him and Jason at the helm will certainly ensure some important continuity and familiarity, but more importantly, we know they are a formidable coaching combination."
(Reporting by Greg Stutchbury; Editing by Toby Davis)
