Re: 63 seaking gale prop spins slow
That is a 63 built by the Gale devision of OMC.Very similar to the Evinrude Johnson motors of that era.An aftermarket service manual covering many brands under 30 hp should serve for you.My aftermarket manual covers the 12 and 15 Gale and E/J motors to 20hp in the same chapter.
Ignition parts and carb kits are readily available for all these 63 motors.
Some right here at iboats under the E/J application.
Most parts interchange.
Most likely you have broken the shear pin(drive pin) or have a
badly spun hub.Pin replacement is simple,a prop shop may be able to repair a spun hub.