Carburetor Adjustment for PWC

Carburetor adjustment is essential for peak performance and longer engine life. The only good way to adjust the carbs is to take the craft to the water, but before you do that you can make some pre-adjustments. Find your low and high speed screws (the low speed is lower on the carb and the high speed is higher). The low speed screw is easy to find and may have a t-handle for ease in turning. The high speed screw may have a plastic cap on it. You will have to remove the cap in order to adjust the carbs (it just pulls off). Once you have located these screws and are familiar with where they are, gather your tools and head to the lake. I also recommend heading for a calm area with little boat traffic as you will be making adjustments on the water.

Tools needed:

  • Flat screwdriver
  • Plug wrench

Parts needed:

  • 1 Pr. NEW Spark Plugs (properly gapped)


  1. With the old plugs in the engine, start the ski and warm it up in the water for about 5 minutes at idle speed.
  2. Once the ski is up to running temperature, remove the old plugs and install a set of new plugs that are gapped correctly.
  3. Take the craft for a low speed ride, no more than 1/4 throttle, for 5 minutes or so then when in a clear area, pull the lanyard and let the ski come to a stop.
  4. Remove the plugs and inspect them. You are looking for a chocolate brown color on the rim of the plug (the end of the metal threaded part that is exposed to combustion). If the color is tan or nonexistent, the fuel air mixture is too lean. If the color is black the mixture is too rich. Turn the screws in (clockwise) to lean the mixture and out (counterclockwise) to richen the mixture. Do this in 1/8 turn increments and repeat step 3 and 4 until the proper mixture is achieved.
  5. The same procedure applies for high speed except you run the craft at 3/4 throttle or greater for at least a couple minutes then pull the lanyard or kill the engine with the stop button without letting off the throttle. When adjusting the high speed screw(s) be very careful and always aim towards rich rather than lean to prevent premature engine damage.
  6. Once low and high mixture screws are properly adjusted, locate the idle speed adjustment. It is the only screw that is attached to the throttle linkage. Turning the screw in will increase rpm, turning out will decrease rpm.
  7. With the ski in the water, turn the idle speed screw until the engine idles smoothly but doesn’t want to take off. You should be able to stand and hold the ski stationary while idling. If you have a tachometer, it should read 1500 RPM in the water. NOTE: out-of-water idle will be significantly higher, some as high as 3000 RPM. If you don’t have a tach but have a speedo, your craft should idle at 2-3 MPH in the water.

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