How to Check the Compression on a Jet Ski

High and low compression in your Jet Ski's engine causes several problems such as engine idle and engine miss. This results in a loss of power and efficiency, along with unnecessarily harsh conditions placed on the engine. Test your own Jet Ski's compression by utilizing a compression tester. This device, used for all gasoline engines including cars, attaches to the spark plug opening and reads the compression in each engine cylinder.

Things You'll Need

  • Socket wrench
  • Compression tester
  • Notepad
  • Pencil
Show More

Instructions

    • 1

      Lift the seat off your Jet Ski to expose the engine. This usually means pulling the seat right off the Jet Ski's frame, but models do vary. As such, inspect the seat to see if any fastening hardware such as screws or snap-on fasteners exist. Remove the seat accordingly.

    • 2

      Unscrew the caps sitting directly over the spark plugs. These caps help fasten the spark plugs in place. Use your hands to unscrew the caps, then place them in a safe location.

    • 3

      Remove the spark plugs with a socket wrench. Apply the wrench over the spark plug, and twist until it loosens from the engine. Place all removed spark plugs with the caps.

    • 4

      Insert the compression tester valve directly into one of the spark plug openings. Turn on the engine for several seconds, and watch the compression tester needle move upward. Turn off the engine when the needle stops moving upward. Record the measurement and repeat for all spark plug openings. This tests the compression in each cylinder.

    • 5

      Compare the compression measurements to the factory specifications outlined in your owner's manual. If you find any deviation, either high or low, take your Jet Ski to a mechanic for inspection to identify the problem. No deviation means your Jet Ski's engine is operating optimally.