The rubber inner bushing inside an outboard propeller’s hub is designed to absorb the shock created by shifting. The rubber hub bushing also serves as a “breakaway” should you strike something, allowing the prop to spin, and so protecting drivetrain components like gears.
Once a hub is spun, there generally remains enough friction to operate at low RPM –sort of a “get home” mode. But, when RPM is increased, the engine revs with little or no boat acceleration because the prop begins to spin. A spun hub feels like a loss of power with excessive RPM.
Sometimes, the hub only spins when the engine revs above a certain RPM, causing many boaters to wonder if they have spun a hub, are experiencing ventilation or cavitation, or are have some kind of gear or power issue with their outboard.
Ignoring tiny nicks in the propeller edge is a big deal. Those nicks can create stress risers, areas that are more prone to crack as the propeller blade works through the water. You can smooth out those areas yourself with a file, but be careful not to grind too much. You'll alter the blade geometry and kill efficiency. Best to let a professional handle that.
Many stainless-steel props are heat treated to improve strength, a process that can make them brittle and susceptible to cracks. Carefully inspect stainless props and look for hairline cracks, especially in the leading and trailing edges. Most props so afflicted can be repaired, but if you don't fix it, you'll end up losing the blade, damage that cannot be repaired. Prevention costs much less than the cure.