Any gearshift electric start motor from 1955 on to 1970 or any pull start from the same period. Yours is missing either the shift or throttle lever (I'm guessing the shift lever) so it would be pull started, shifted on the motor then accelerated with the lever. If it is electric start the wiring bundle would be connected to the start switch and choke button.
Quicksilver was the olde tyme word for Mercury.