Good morning William,

When it happened to me (same thing: propeller still on bow thruster - but no movement and screaming sound) it was the bearing inside the foot that were worn out.
Here are pictures: http://www.nikimat.com/bow_thruster_spin.html

You will need from Amel Part 1110 (Mecanism Pied de Propulseur SM) the price varies a lot if you purchase it from Martinique (977 Euro) or La Rochelle (582 Euro)
scroll down to 1110 to see the part:
http://www.nikimat.com/spare_parts_bow_thruster.html

NOTE: Make sure you order with the Tufnol shaft and not the bearing by themselves as the size of that shaft has changed (look at the last picture on: http://www.nikimat.com/bow_thruster_lost_propeller.html )

NOTE 2: when you receive the 1110 - the small open space to receive the key on the small gear will have to be machined a little as it is not thick enough.
If you look at the 2nd picture on http://www.nikimat.com/bow_thruster_spin.html
You will see where the key goes has not be machine as much as on the old gear.
You have a good view on picture 6.

Wood luck, sincerely, Alexandre

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