that is not cavitation/ventilation.
its poor paint on the prop and nothing to worry about.
cavitation burns on a prop are normally in a different area to that in the first picture of the prop.
what your seeing the area that is getting the most pressure from the water leaving the blades.
its just where the outer cup is, this is the part that has to travel the furthest on each revolution and the water at that point is at the most pressure when leaving the blade.
Most alloy props have this to a certain extent, especially those with the least amount of paint.
Most white props seem to get this more than the black or grey props, I honestly have never seen a white prop with as much paint on as dark props.
the OMC alloy props have a pretty heavy black coating on them that is also hard to get off, a Yamaha props is easy to scratch the paint off.
The loose prop nut is because it was not tightened up when put on.
40ft pounds is madness to tighten a prop, I never go much more than about 10ft pounds then put the split pin in the nut and never have a problem.
