Disassembly
Remove the unit from the boat: first, remove the small split pins which secure the swivel end fittings at the end of the throttle (centre line) and gear (side) cables to the selector arms, then slide the cables out from the body of the unit.
1 Detach the front control arm by loosening the retaining grub screw underneath and pull this forward off the splined shaft. Gentle tapping of the control arm may be required, but ensure the unit is in gear – ie, NOT in upright-neutral position. If the arm is stubborn, as in my case, then it may be necessary to cut the unit from its mount and apply penetrating oil into the back of the control arm until it can be freed off. Do NOT strike the red central button directly or you will risk damaging the gear pin, like I did!
2 Expose the back of the unit with the six blind rivet heads by removing the two machine screws (and washers) with their throttle and gear selector plates. The six flat rivet heads are now carefully centre-punched and drilled out to a depth of 5mm with a 5mm drill bit – ideally using a pillar drill with the unit held firmly in a wood block.
3 Using a small flat-bladed screwdriver, the two halves of the unit can now be gently prised apart, exposing the contents of the unit.
4 A short gear pin transverses the drive shaft which is spring-loaded to the red button. This pin commonly gets bent and jams the control arm. First remove the circlip holding the cog in place on the shaft then it can be lifted out, giving access to the short pin which lies underneath. This may require some straightening before it can be removed. Once removed, the pin needs to be fully straightened and replaced on the shaft, followed by the large cog and its retaining circlip.