That's "old" (pre-25XD model) - 1982.
Nothing listed in Merc's active parts. Can't even find the kit (and probably did exist) in the discontinued listings.
Your best bet may be to get the components from a outboard recycler.
You can try Twin City Outboards
http://www.twincityoutboard.com/
I would get their number from their website, give them a call. If they can't help maybe they can point you to someone who can.
It could end up costing "significant bucks", not just for the remote engine connection parts (if they can be found) but then add in a steering system and control box and you could easily drop a few hundred bucks real quick (200 might only cover the steering).
I don't know if I would consider that on a motor of that age. It's not a "classic" yet and if some of the most minor things go "flooey", it's next to impossible to get parts.
You could end up with a 130 pound paperweight and a set of "remote parts" that fit nothing newer (save the steering).
Just my 2 cents
