I think you need more details on exactly what repairs were done. If a lot of water got into the outdrive it needs to be completely disassembled. All gears and bearings examined for rust or other damage and then the drive out back together with new seals.
I am assuming what was replaced was the transom housing. Which is what the outdrive is bolted to.
Seems odd that any one bolt breaking off would cause significant damage or allow water into the the engine area.
