I GOT IT!!!!!

[spareparts]

a proper line up shaft should be a tighter fit, but back when OMC was making the cobra, the line up shaft they used was a whole lot smaller than the merc( used the same spline size and diameter), you could line up an engine with an OMC shaft, and the merc shaft wasn't even close to fitting. If you use teh old shaft, you may have to weld a handle on it so you'll have something to grab when you pull it out