I would like to confirm that I believe that it is important to exert pressure only on the slotted shaft and shaft and not to apply pressure to the gearbox housing or, perhaps even more importantly, the aluminum bracket of the main boom to which the gearbox attaches. Both of those items are aluminum whereas the shaft and the slotted shaft are steel. When using any type of pusher/puller it is important that the pressure/counter-pressure be applied only to the steel parts involved and not to the seals, bearings, housings, or other parts lest those parts be damaged or distorted. For the same reason I recommend agains "hammering" with large hammers against the inner shaft as a method of removal.
I have found that with annual removal and re-greasing of the outhaul shaft, all that is required is either just pushing the shaft out by hand or at the max very light tapping with a hammer against the bolt that I thread into the threaded lower aspect of the shaft. In my opinion, re-greasing every 6 months is probably over doing it a bit (no harm but annual is adequate in my experience).
All the best to all who own Amel boats. f
Gary S. SIlver
Amel SM 2000 #335