The crack is right where the taper starts. The photo lighting may be a bit off. Both parts seam to be the same color. Does the axle need to be replaced or can the spindle only be replaced? From what I've seen on the web, it looks like the whole axle.
My 2nd on maybe a pressed-on sleeve...look at it very closely before maybe repair/replace a perfectly good spindle?It sure looks cracked. But what gets me is the tapered area is a different color... almost looks like a sleeve pressed onto the spindle. And that crack would be the seam. Dunno... just throwing it out there. Hard to tell from a pic.
Thats pressed on - NO CRACK ----- GO BOATING!