Stainless will rust and tarnish if there has been any excessive heat, I think the new ProXS which I own a 225 4.6 liter V8, I have to be careful to keep lower end 4 cooling ports clear, heat has early on shown itself on the Mercury and the Fury forged areas. I had an electrolysis issue because the dealer wired my ultex backwards, everything has been fixed and or replaced such as the shaft and lower end on the ultex. They took the prop off and sent it for polishing, they got the heat discoloration issues out but I finished by hand polishing with a good metal polish, it now looks brand new. I was a metallurgist and independent contract welder, I have been exposed to a lot of heat treating, torch work using heat, etc. I agree with Tim, no SS prop should look like that.