(assume we are talking about a "model 200" 20 horse since Merc's largest motor in 1973 was a 150 horse)
I looked up the remote attaching kit (engine end bit's and pieces that would be required) and it has been long discontinued.
Merc part (46455A3 - kit "E" number "4") sold for about 120 bucks - you may be able to find it is some dealers "old stock".
You would still need a set of controls and cables to go with that - the kit is just the little connectors.
Just about any modern steering system would easily retro-fit.
Teleflex and UFlex both sell "steering in a box" set-up starting at about 150 bucks with everything you need except the steering arm for the motor end.
Even with a basic remote (new upwards of 200 bucks), and assuming you can find the attaching kit or jury rig something up yourself, you could easily drop 500 bucks converting this motor over and getting it rigged up.
Personally I don't know if I would invest that much into a motor of that vintage. If it was a "post-1986" model at least all the components would be "modern".
Even if the motor is in perfect running condition, it's total value is probably somewhat less than the cost of this retrofit would be.
Only you can decide if converting to remote is worth the cost, which would still leave you with a motor worth somewhat less than 500 bucks even after the upgrade...
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