A friend of mine is pulling his old 100 Hp johnson and replacing it
with a similar V4 johnson he bought used. He knows very little about
working on outboards. I know just maybe a little more than he does.

The mounts look exactly the same. Same looking motors (I cant remember
what year both are early 80s). Besides making sure the holes line up
on the transom. That all the ajustment pin points are the same on the
motor to be installed.. And knowing how to hook everything back up is
there anything else I should consider here? Is it pretty
straightforward? Any common mistakes here?

How about the picking up of the old motor? Where to attach the
come-along or cherry pick to to pick it off the transom?