Re: i have a chance to buy a merc
Quicksilver/Mercury made two lever controls, no bells and whistles, just two levers back in those days. If you had an electric start engine you could get one with a key start switch mounted in the rear of it with a wiring harness. You can find one if you get on the www and start looking. I have seen them. Might be sure that you get one that fits the side your steering wheel is on (starboard side in today's market). Back then Port mounting was "the thing" and you may not be able to disassemble a Port mount and reverse the levers so that it will work on the Starboard side.
HTH,
Mark