I have personally never worked on that particular motor but I have a 1959 OMC 35hp. I'd imagine they are pretty similar which would mean it would be very easy to work on. My advice would be to create an account on iboats . com and post in the Johnson/Evinrude repair forum. There are a tons of guys on there who focus solely on the old 50's to 70's OMC motors.

Based off what you said about the carb spilling gas, you probably have an issue with the float sticking or something causing your needle valve to not fully close.

No matter what it is the first steps are always to check spark and compression, even if it sometimes runs perfectly fine. If they check out then it is fuel related. For an old motor like that, depending on the last overhaul, I'd go ahead and rebuild the entire fuel system from the tank hose to the carb. New fuel line, primer bulb, fuel pump rebuild, fuel filter, and carb kit would all be in order and would cost $50 or less depending on if you needed a new primer bulb or not (they seem really expensive to me). Then dial in the carb per the instructions in the sticky thread on iboats and you likely will have a problem free motor again.

BTW, both our motors are covered under the same Clymer manual and you can get them used on Amazon for dirt cheap. I just got a used one in perfect condition for less than $5 shipped to my door.