Is there any precaution I should know about when mounting an outboard
to an aluminum hull? Do I need to put something between the two metals
or does it matter?

Also, does the bolts needs to be coated with anything special prior to
insertion? Lastly, what do I do with the old holes? I can't keep the
old bolts in the hole as the bolt head will contact the mounting plates
of the new outboard. Would 5200 be sufficient to fill the holes?
Thanks!