Mooring Lines recommendations at AP
under 30 feet use 1/2" line
30 feet to 40 feet use 5/8" line
40 feet to 70 feet use 3/4" line
70 feet to 90 feet use 7/8" line
90 feet to 110 feet use 1" line
As a general rule, the length of bow and stern lines should equal two-thirds of your boat's overall length. Spring lines should be slightly longer, approximately the same length as your boat. Unless your boat is unusually heavy or will be subjected to severe conditions, a bow line, stern line, and two spring lines are recommended. If your permanent slip has outboard pilings as well, you will need an additional bow and stern line.