How to Adjust Carburetors on Boats
- 1). Launch the boat and allow the motor's temperature to normalize. Release the latch that holds the top cover of the outboard. Lift the cover off the engine and set it aside.
- 2). Put the engine into the "Forward" gear and glance at the tachometer. If the idle isn't between 900 and 1,000 rpm, locate the throttle stop screw on the top of the carburetor, opposite the fuel inlet line. Turn the screw with a screwdriver, counterclockwise to lower the idle speed and clockwise to raise the idle speed, until it falls between 900 and 1,000 rpm.
- 3). Run the engine up to its recommended maximum rpm and hold it there for 60 seconds. Release the throttle and allow the motor's speed to drop precipitously.
- 4). Turn the low-speed needle, located on top of the carburetor, on the same side as the fuel inlet line, counterclockwise about 20 degrees, if the engine doesn't change speeds smoothly. Wait 15 seconds, increase the engine's speed once more and, once again, let it drop suddenly. If additional changes are needed, wait 15 seconds between each adjustment.
- 5). Shut the engine off once it changes speed smoothly when the speed is allowed to drop suddenly. Replace the engine cover.
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