Well you got one sweet motor there, I love them, have 1 or 2
Bad news is that there will be some consumable items that will need to be replaced, good news is that those motors are bulletproof and with a little sweat and equity should be a great runner.
Start with a compression test, the compression will hopefully be in the 100-140 psi range, most importantly even between cylinders.
If the compression tests out, time to start inspecting/replacing parts.
Start with the ignition. Remove the recoil and the magneto inspection panel on the flywheel. Turn the flywheel clockwise and inspect the ignition. Has it been updated, OR are the coils original and cracked? If they are original/cracked dont bother testing them, just remove the flywheel and replace. They are no good, I guarantee it. We can get more detailed on the ignition when time comes.
After done, retorque the flywheel and pull the carb. It will need to be dissasembled and soaked in carb cleaner. The old fuel left in the carb will be varnished. After a soaking, blow out all the passages with carb cleaner, wash with soap and water, then blast dry with compressed air. Once clean, install a carb kit and reinstall on motor.
It is now time to drop the lower unit and change the impeller in the water pump. They are made of rubber and dry rot/crack. It needs to be replaced, it is a vital piece which keeps the powerhead cool.
Replace the gear oil with fresh along with new washers on the drain/vent screw. If it is milky there is water intrusion and the gearcase will need to be resealed. They may need to be even if the oil is black but you wont know without water testing or pressure testing it.
Enjoy her for the next 50 years
Just a quick rundown of restoring one of these antiques, once you are ready we can go into more detail. A Service manual and parts manual will be necessary, we can help with that.
Post a pic....we love them pictures