Thank you to Alexandre, Bill and Judy.
I'll try to give answers.
As I wrote the Amel Sharki is hull no 173 1989.
The bow thruster is a Bison from "Propulseur d'etrave Martine - Hyeres". This company ceased the activity.
The pin is released. this is the first thing I checked as I forgot it already in different occasion (sic)
All the electrical is OK. The small arm releasing the cable come up and the propeller works.
The bigger arm containing the shaft and the propeller is stuck on the top position.
I suspect because of corrosion or other obstruction which prevent the arm to fall down by gravity.
My concern is that forcing the arm down I could damage the gasket for water retention as in the Sharki, which is much smaller than SM or 53, the thruster is below the floating line.
That's why I am looking for spare parts particularly for the gasket.
In any case thank you for your immediate help.
Sharki no 173
Riva Ligure (Imperia- Italy)