Thanks for your reply !
The manuals of the engine finally came in so I learned more. After some discussion with Barrelback owners they adviced me to use the engine with direct drive (as you also suggested). If it's possible (!) I will try to reconfigure the drive into a direct drive.
What kind of adaptions to the hydraulic reverse drive can I expect when I remove the gear reduction. Are the necessary parts still available or do I have a problem ?
Thanks again for your help.