When we were at Chantiers Amel - Caraïbes in Martinique we removed the outhaul motor which came out easily with a puller tool they supplied  They did not have the replacement rubber inserts but instead supplied us with short lengths of rubber tubing and nylon washers.  The tubing spread to fill the hole (ours looked like they were still round.  The right size tubing compressed vertically and expanding horizontally might do a good job in this situation.  Photos-- (included a pic of the puller, the cleaned up shaft with the bronze collar as well as the inserts-- https://photos.app.goo.gl/RLit2YvNU5BxQDjt6

Brackets vary by SM model/year but the rubber inserts should work.  Amel had us remove the gearbox and motor after lending us the tool and we used them to service and rebuild the gearbox and electric motor.  We replaced them ourselves.

The rubber insert is shown before being tightened down.  Note that we used Tef-Gel anti-seize on the shaft and key before reassembling--we will follow-up with a report when we next remove the shaft from the gear box.

Bob and Suzanne, KAIMI SM429