Cylinder Compression - Periodic Maintenance
Normal Compression:
- Standard: 1000 - 1400 kPa (10 - 14 kg/cm2, 142 - 199 psi)
- Max. difference between any other cylinders: 100 kPa (1.0 kg/cm2, 14 psi)
Low compression pressure can indicate one or more of the following:
- Excessively worn cylinder wall
- Worn piston or piston rings
- Stuck piston rings
- Poor seating of valves
- Ruptured or otherwise damaged cylinder head gasket
Test Procedure
- Start engine and allow to warm up, then shut engine off.
- Remove the STBD/PORT engine side lower cover.
- Remove all spark plugs.
- Install the compression gauge into the plug hole.
- 09915-64510: Compression gauge
- 09915-63210: Compression gauge adaptor
- Disconnect the safety lanyard from the emergency stop switch.
- Disconnect the remote control throttle cable from the throttle lever. (R model)
- Disconnect the throttle limiter rod from throttle drum. (Tiller handle model)
- Move and hold the throttle lever in the full-open position. (R model)
- Move and hold the throttle control grip in the full-open position. (Tiller handle model)
- While cranking the engine with the starter motor or recoil starter, note the maximum compression pressure reading on the gauge for each cylinder.
- Reinstall parts removed earlier. (spark plug, side lower cover, etc.)
WARNING: Disconnect the safety lanyard from the emergency stop switch prior to cranking the engine. This will prevent any residual fuel discharged from the cylinders from being ignited by a spark discharged from the spark plug cap.
