A short story about what happens when you hit a hard object in the water (rock). Most off the outboard brands have a protection system that makes sure the impact does not damage the engine. Here is an example, the pictures show how the drive sleeve and adapter look after.
The plastic teeth on the left are originally straight. The impact made the propeller stop instantly and damaged the sleeve / adapter, this is supposed to happen.
Replacement is fast and easy.
(This is an example of a Mercury engine)