Hi Norbert, I am sorry that you are having issues, yours is not a problem that I have come across, but to find the 2 clips not located would suggest an issue with the spring washers or excessive wear resulting in excess end float in the shaft. It should not matter which position the gear
selector is in, the tool we made gripped the very top of the shaft to prevent it moving down, the bolts in the tool pushed down against the spring washers allowing the clips to be inserted. From what you have said, in certain gear
positions, you have too much play in the top of the shaft allowing the lock rings to come out, this should clearly not be possible, which would suggest a potential weakness in the spring washers and they may need replacement.
Is your boat
is coming out of the water
soon? If so, it may be easier to take the saildrive
out, and take the gearbox
off of it, this way you can hold the shaft without needing a special tool, you can then check the condition of the sliding sleeve/cones and put new spring washers in.
Sorry I cannot be of any more help.