Other than what the others have said, the throttle and shift cable may need
adjusting for the different engine.
Make sure the shift cable is adjusted so you have good forward, reverse, and
neutral engagement. You can check this in the driveway by having someone
spin the prop w/ their foot while shifting. Should engage solid and
disingage with no clicking.
Make sure the throttle cable is adjusted so when in neutral it is tight
against the idle stop and when full throttle the throttle plates are level.
You might also find that you need to adjust the idle speed once you get it
in the water. Should be set for 600 to 800 rpms in gear at idle in the
water. Lower is always better as long as it will run smooth and not die
when you shift into gear. This will be about 1000 in neutral usually but
again, adjust for in gear.

--
Tony
my boats at http://t.thomas.home.mchsi.com



wrote in message
...
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?