N Andover > Gloucester, Rockport
This route is ~45 miles, and add another 28 miles or so if you ride back by retracing Rt 133, etc., from the end point to the start point. For a 70+ mile ride, you may want to have some friends along and so this route starts at Drummond Park on Milk Street which is a convenient place to meet.
The stretch of Rt 133 between Ipswich, through Essex, and into Gloucester is a nice road for bikers. The surface is in good condition and it's wide enough that motor vehicle traffic isn't an issue.
Rt 127A and RT 127 in Rockport is scenic, but the road is thin in places and people sometimes drive too fast. Use caution.