Re: 70s johnson 50 been sitting for 10 years
Remove the plugs (one at a time so you put the wires back in the right place)
Put a few tablespoons of marine outboard 2-stroke oil (best price is fr iBoats, $4.69/qt) in each cylinder
DO NOT USE LAWNMOWER 2-stroke oil
If it is a 4-stroke, use marine 4-stroke oil for above
Rebuiild carbs w new floats, new plugs, replace impeller. If you have CDI it saves the ignition work. Replace lower shaft oil and seals if it leaks
Go fishing
Run it for the first time w 16:1 to get the bottom end well lubed