1965 40HP idle problem

[bobfreer]

Recently purchased a 1965 Glasspar G3 with a Johnson 40HP motor. It starts easily but willnot idle slow enough to keep running.
I have checked fuel filter and changed plugs. Fuel and oil is fresh.
Squeezing fuel bulb causes fuel to leak from carb throat. Float may not be shutting but I don't have setting insstructions. At low RPM motor jerks as if it were running on one cylinder. Smooths out as RPM increases. I've been unable to find a step-by-step procedure to trouble shoot this problem.
I'm a reasonably good mechanic and have tools and basic test equipment if someone can offer suggestions.
Thanks

[boats.net]

Unfortunately because of the year, you are going to have a hard time finding specifications for that motor. It does sound like your carburetor needs repair. Depending on the severity of the situation, you may be able to repair without parts. The following link may assist you in obtaining a service manual if you require.
Original outboard product and service manuals for Johnson, Evinrude, Gale, and OMC