Re: 63 Merc 3.9hp no spark
Pull the flywheel, clean the points to bare metal, polish with Crocus Cloth, degrease and gap the points to .020".
Use a harmonic balancer puller and (3) Grade 8 bolts of appropriate length/size to fit the puller holes in the flywheel.
Torque the flywheel nut to 35 ft-lbs and you should be ready to go!
Note: probably gonna need an impeller, too! Not to mention a little carb cleaning unless you were lucky enough to find one that was properly layed-up.
Here's one place you'll find parts diagrams, etc:
Mercury Marine 39 (1 CYL.) Outboard Motor Parts by Component
HTH...........ed