JD, the length of line is determined by the depth of water that you're fishing and the type of line and lure you're using. If you're trolling for Striper, you're probably running about 2 knots when using tube and worm rig of somekind. Normally, I use either lead core (preferred) or wire to get the lure down....every color of leadcore is about 10 yards and rule of thumb is 10 yards will get you 5 feet of depth, depending on speed. If you troll with Rapala type plugs or an umbrella rig, you may go a bit faster which will require a little more line. If you use straight mono, you'll need at least double, maybe triple the output of line to get any depth unless you add a keel weight on the rig. Try and keep the rig out your wake if possible.