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Carb and throttle adj.

I have a 82 wellcraft with a 260 mercruiser i just got a new carb rodchester 4bbl i start the engine it idles at 2000 rpm i need to know how to adj. the carb and cable

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Here is how to do it. First disconnect the throttle cable to the carb and let it hang loose. Make sure the outdrive is in neutral and the boat is secured to the dock or on a trailer with a water ****.

Pull back on the throttle by hand directly on the carb throttle shaft. Observe the Choke cam on the opposite side of the Carb. Let go of the Carb throttle shaft and see where the Stepup Cam is set. The Choke plate should be closed most of the way. You will not have very much time to make an adjustment.

Start the engine and let the Choke work and observe the RPM. There are usually adjustments you can make to put the Stepup Cam on a lower step by bending the Link Rod if it is running too high in Choke. Sometimes the Cam is left alone and a screw similar to the Curb Idle screw on the Throttle side just needs reduction to ride lower on the Choke Cam.

After the Choke is warm, it disengages with a pull on the Throttle. Now you are using the Throttle side of the Carb to operate the engine RPM. You want a low RPM for sake of the outdrive gears and NO WAKE zone. The adjustment screw opens the Throttle shaft, You set it for the Manufacturers Spec. probably 550 RPM.

The Throttle cable is now adjusted so it pushes slightly against the Carb. This forces the throttle closed. The Throttle cable has threads and a sort of Knurled knob which runs on these threads. This device is used to lengthen or shorten the cable so that pressure is applied against the Throttle.

When the outdrive is in water you will has resistence on the Exhaust. This will slow the RPM. If the motor stalls you will need to adjust the motor to idle Specs while in the water.

For best economy, find a Vacuum port and attach a Vacuum guage to it and adjust the air mix to the highest Vacuum reading then turn in the Mixture screws slightly until the vacuum starts to drop.

Posted on Jun 04, 2010


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