Last summer we did the reverse from Ottawa to Acadia National Park with stops in Montreal and Conway NH.
From I95 north of Portland take US302 into New Hampshire and the White Mountains. Good roads and some very memorable scenery that has the area on our short list for a return. Two lane roads but July traffic was light and made for an easy drive. In the White Mountains there are some hill climbs that will get your attention so take your time. Lots of campgrounds in the area.
Once thru the White Mountains head towards I91 north which will change to 55 once north of the border. Switch over to 10 west towards Montreal. Just east of Montreal change over to route 30 which will loop around Montreal and get you to 40.
Once you cross into Ontario 40 changes to 417 which you can take to Ottawa. If you want to try the road less traveled get off 417 and on 17 which follows the Ottawa River and will merge back with 417 east of Ottawa.
2006 Hurricane 31D built on a 2006 Ford F53