if your props spin inwards toe out, if they spin outwards toe in. 1/8 to 1/4 inch is fine. The reason is that the lower half of the prop is in denser water and therefore exerts more lateral force on the drive tending to pull it inward or outward depending on the rotation. One of the main reasons to "toe" the drives is so they will be as close to straight as possible and therefore cause the least amount of drag while running. 1/8-1/4" total toe, sum of both drives. Measure the front of one drive to the other and then the rear of the drives, the rears should be wider or narrower depending on your rotation than the fronts. If you find your boat to be handling strangely sometimes toe adjustments can help. Not all boats run happily with perfectly straight drives.