How to Sync an Outboard Carb

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When you sync an outboard motor's carb, you adjust its linkage so that it performs in concert with the other carburetors on the motor. The carburetors on any engine with multiple carburetors must be synchronized so they operate as a single carburetor. Once the carburetors are synchronized, all of the outboard's carburetors will deliver a similar flow of fuel and air mixture to all cylinders, simultaneously. This balanced flow of fuel will help to ensure that your outboard motor operates at optimum levels.

Items you will need

  • Screwdriver

  • 5/16-inch box-end wrench

Locate the throttle cam follower roller, near the end of the throttle shaft and connected to the carburetor-end of the throttle cable of both carburetors. Loosen the roller adjustment screw with a screwdriver and separate the throttle cam from the follower roller on each carburetor.

Locate the upper carburetor's lever adjustment screw on each carburetor and loosen it.

Rotate all the throttle shafts a bit, permitting them to snap shut. Push upward gently on the adjustment tab, found on the bottom of the throttle cam, where the throttle shaft connects to it, to prevent its movement. Thread the adjustment screw back into place and tighten it.

Ask an assistant to move the remote throttle handle, at the boat's control station, slowly. As your assistant does this, watch the throttle shafts to ensure they begin to rotate at exactly the same time. If not, readjust them until they do so.


  • Disconnect the negative cable of your battery before performing any maintenance work on your outboard motor, this will prevent electrical shock or accidental starting. Remove the nut from the negative post with a 5/16-inch box-end wrench. Lift the cable from your battery, move it outside of the battery box and close the lid of the battery box. After the work is complete, reconnect the negative battery cable.


  • Insert the blade of the screwdriver into the slot machined across the top of the head of the screw. Put a slight downward pressure on the screwdriver to prevent the blade from riding up and out of the slot as you turn the screwdriver to the left, or counterclockwise, to loosen the screw, or as you turn the screwdriver to the right, or clockwise, to tighten the screw. Remember, "righty-tighty, lefty-loosey."
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