Mercruiser 470 camshaft issue

[TSCHAEFF3]

I bought a new cam for my Mercruiser 470. The new cam is 23 5/8 inches in length with a threaded opening on the front. The old cam is 23 5/8 inches from the rear to the beginning of the beveled area on the front. There is a threaded shaft that looks like it may screw into the cam. I am finding no info online.

 

[Bt Doctur]

some had the impeller held by a bolt, some had the impeller screwed onto the cam