Raymarine Autohelm 100 Install Manual page 52

Chapter 2: Installation 51
D759-1
Both sprockets must be accurately aligned to run in the same plane.
Correct alignment must be carefully checked by means of a straight edge.
The gearbox can be mounted in any position. Additionally, the drive
sprocket may face in any direction as the steering sense can, by reversing
the polarity of the drive motor connection, be corrected when installation is
complete.
Finally, the chain should be tensioned until it is just tight and there is
minimal lost motion to the drive system. Total lost motion between the
driven sprocket attached to the steering system and the rudder stock
should not, under any circumstances, exceed 2% of the total movement.
If lost motion exceeds this level it must be corrected, otherwise steering
performance will be impaired.
Having completed installation of the drive unit, turn the steering wheel from
hardover to hardover and check that the chain and sprockets driving the
actuator move freely and are in alignment.