Yup, the first 3 years (starting in 1997), the Boxster was available only with the 2.5 engine. In 2000, Porsche upped the standard model to 2.7 and introduced the 'S' model, with the 3.2.
So it's either not a '97, or it's not actually a 2.7 (unless the original one was swapped out).
Also, there was no 6 speed manual available until 2000.
Check out:
http://autos.msn.com/research/vip/default.aspx?make=Porsche&model=Boxster&src=LeftNav
Gives info on each year, from '97 to '07.