Using the right rope for docklines is a must. You shouldn’t use leftover or old sheets or halyards, since these low stretch lines can put years of wear and tear on your boat in no time. Nylon is the best choice for docking as it is durable and fairly UV stable, and provides good stretch characteristics regardless of single or double braid constructions. Boats under 20’ generally require 3/8” line; 20’-40’ boats, 1/2”; 40’-55’, 5/8”; and 55’-65’, 3/4”. If your boat is heavier than average, or has greater windage, you may want to choose the next rope size up.
As a general rule, fore and aft dock lines should equal two-thirds of the boat’s overall length. Spring lines should be approximately the same length as the boat. Unless the boat is unusually heavy or subject to severe conditions, two bow lines, two stern lines, and the spring lines are recommended. Spring lines keep the boat snugly near the dock by preventing it from moving fore or aft, while allowing for the rise and fall of the tide.
Tow ropes need to be floating and be visible lines. Lightweight polypropylene is non water absorbing and will float at the surface to avoid any entanglements with props or rudders. Light colors stand out against the water to ensure you never get a bow line stuck in your prop again.