It is 190 miles from Boston to New York. The Acela take 3.5 hours.
That is 54 MPH
DC is about 200 from NYC and it takes 2 hours and 45 minutes
That is 72 MPH if you don't stop in Philadelphia.
Most of the Acelas I've been on make at least one stop in the Baltimore
area, sometimes two, then a stop in Delaware, Philly, Newark, before
arriving at Penn station. I'd have the Acela stop only in Philly between
here and NYC, and with high speed trackage and equipment. Under two
hours, portal to portal.
New York City usually is a 4 to 5 hour drive from DC, depending on road
maintenance and traffic. At least 250 miles from where I live.