Cutless bearing support

[Coastalrunner]

I'm probably going to come across as a pain, but I'm full of questions?

So my seavee spins a 18x21L 4 blade wheel, so does my albin. I attempted to replace the albins with a spare from the seavee. But it would not fit, the planes on the spare end beyond the hub of the prop. Because this it was to close to the rudder. My question is, how much shaft is suppose to be exposed. I thought the rule of thumb was 10-15% of prop diameter, just like tip to hull Clearance. My has roughly 6" of shaft beyond the cutlass before the prop. That sound like way to much. If it was 2" I could move the shaft forward and swing a better wheel with more surface area.

Anybody else notice this?