QD-24 = 1963 10hp Johnson. Mixture is 24/1 (1qt 50/1 oil to 6gal gas), 87 octane gas is fine. Spark plugs = Champion J4C or J6C gapped at .030. Points set to .020. Gearcase lube is Hi Vis.
First, check for proper compression, then with the spark plugs removed, check for proper spark which should jump a 1/4" gap on that model with a strong blue lightning like flame... a real SNAP!
If the above is okay, the usual hard starting problem is a fouled carburetor. Remove, clean, and rebuild it with a complete carburetor repair kit.
The small hole at the cavitation plate is simply a water drain hole. Check the gearcase lube. DO NOT remove the philips screw from the skeg as that is a long shoulder bolt which is a pivot rod for the internal shift lever. If the gearcase lube is a milky substance, that is oil mixed with water and the leakage area will require correcting.
(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)
Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.
Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.
Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.
When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.
(Checking Gearcase For Leaks)
(J.Reeves)
Remove the large slotted drain/fill screw from the bottom of the gearcase and also the identical looking screw that will be located up near the cavitation plate in order to drain the gearlube.
After all of the lubricant has drained, install one of the slotted screws, whichever your preference might be.
Apply 7 to 12 pounds of air pressure to the open screw hole. Use a piece of rubber fuel line or something to create a tight air hose fit if you do not have a proper fitting.
If a leak exists, that pressure should allow you to locate the leak by sound and/or sight.