This could become something akin to the which gear lube to use? question, with no one right answer. I have always used two springs, one on each cable end, but I did some extensive upfitting this year on a 14′ aluminum side console boat with a 45 cid Evinrude 40 and discovered that having two springs resulted in soft, vague steering response. I removed the spring on the high tension side (flywheel and propeller torque) and added a thimble in the cable loop, effectively removing any slack or spring action. It made a big difference. Of course, the cable routing was such that a single spring could compensate when the motor was turned or tilted.