See full version: How to Adjust the Fuel Mixture on a Johnson Outboard
Remove the engine cowling as per the instructions in your Johnson outboard motor owner’s manual. When doing this, you will possibly be exposed to moving parts that are normally enclosed by the engine cowling. Be sure you do not have on a loose shirt or, that you are wearing anything that could become caught in the engine. here
Locate the engine carburetor per the owner’s manual. Locate the “idle adjustment” screw per the owner’s manual. It will likely be at the base of the carburetor, but may vary by engine design. [links]
It is important to make sure the fuel mixture on your Johnson outboard motor is set correctly. If the fuel mixture is off, your engine will not run as smoothly or as efficiently as it could. In the short-term this could cost you money in increased fuel consumption. Over the long-term, it may cause damage to the outboard motor resulting in costly repairs or even replacement long before you would normally need to. Adjusting the fuel mixture on your Johnson outboard is a fairly easy process to do. more
Start the Johnson outboard motor. Let it idle for a few minutes to warm up.
Turn the screw using a slot screwdriver until the engine reaches a smooth idle, where it is neither sputtering as a result of a lean fuel/air mix or has a strong smell of fuel from the engine running rich. The adjustment is fairly small ranging from a quarter to one full turn only. [links]
I paid $15.49, this kit did not include float. If needed, you can buy it separately for about $3.00 [links]
Carb Kit NAPA Part Number 18-7043 or replacement for OMC Part Number 382047, 3832049, 383062, 383067, or 398532 [links]
The carburetor is a simple, cheap, and time proven-device which properly mixes air and fuel before it enters the combustion chamber for ignition. The carburetor for this motor is the same carburetor that is used on many outboard motors and even Lawn-Boy lawnmowers. There are many small parts which you do not want to loose so it is best to have a clean and organized work area.
The carburetor mixes the correct proportions of air and fuel into an atomized mixture. The amount of fuel/air mixture that is allowed into the cylinders determines the speed and power. The fuel and air are mixed in the venturi, commonly called a barrel. This simple carburetor has only one barrel. The venturi is simply a carefully sized restriction in the carburetor through which air that is being sucked into the engine must pass. As the air passes through this restriction, it speeds up causing lower pressure to suck fuel through a jet that releases fuel inside the venturi where it turns into a vapor. The jet draws its fuel from the carburetor bowl which contains a small reservoir of fuel in the carburetor bowl. The amount of fuel in the carburetor bowl is controlled by the float and float valve assembly that keeps the bowl full of fuel. A high and low-speed needle valves adjust the ratio of fuel to air within small limits. The volume of air entering the carburetor barrel is controlled by a butterfly valve which is twisted open by the throttle lever. here
Johnson Seahorse 5.5 Carburetor Exploded View [links]
The carburetor is part of the overall Fuel System which starts at the gas tank and fuel line. The tank that came with these 50's era motors were dual line pressurized tanks. OMC eventually got away from using pressurized tanks in the 60's and went to single line suction tanks. Given the condition of my tank and fuel lines, I decided to convert to a more modern single line tank by adding a Mikuni vacuum fuel pump, which I bought on-line for about $22.00, and swapping out the fuel line connector to the single line type. CLICK HERE to see a description and pictures of my upgrade project.to the newer tanks. If you are intent on keeping everything original on your motor, then there are kits available to replace the lines, connectors, and seals for your pressure tanks.
As long as the float arms aren’t corroded, bent, etc., and will perform their function, it should be okay.
Could not get all the pics in the post here are a couple more more
Bucaneer, thanks for the diagram. Funny thing is, the diagram does not show the inside of the inside of the upper half of the carb where the inlet needle seat is located and the float is attached. Either way, I was able to get everything apart but the inlet needle seat that sits behind the float. I was able to get both the other needles out along with the seals that go in there as well. I may have to get that half of the carb body because the ears for the float pin are slightly broken. One is open towards the float in this direction –> and the other is open in this direction ^ .. When I opened it up it looked like the pin was in good position and the old float did move back and forth. I am hoping that I wont have to replace it and will check by putting in the new pin with the new float and see if it will hold. If not I will need to get at least half of a new carb. more
Next, light sand the surface using 300 grit wet & dry paper. Be careful to avoid cutting into the cork and reducing it's mass. Just lightly sand the shellac so the new coating will adhere a clean surface. more
After removal of the High Speed Jet and Primer Pump assemblies from the carb body, the brass tube, plunger washers and leather seals will undoubtedly remain in the primer cylinder. At this point, some fabrication of extraction tools is required. here
By David Poche
Drawing of Primer Pump and High Speed Jet Assemblies from a Johnson service manual. here