Compression Testing 2004 Suzuki 40HP Engine

Compression testing the 2004 Suzuki 40HP engine is a test method used for measuring the compacting force or crush resistance of each engine’s cylinder and the ability of the piston to recover after a specified compressive force into space is applied and even held over a defined amount of time. The compression test can be used analyze the performance or to diagnose internal engine problems. Follow the step-by-step procedures for verifying the compression on the 2004 Suzuki 40HP engine. Need a repair manual? Download one instantly here: http://www.inboardrepairmanual.com/?p=250

2004 Suzuki 40HP Compression Test

Compression testing is important to evaluate engine performance. A 2004 40HP Suzuki outboard motor with scored cylinder walls, broken piston rings or damaged pistons won’t perform properly. This how-to-guide requires basic mechanical machine knowledge and use of tools to correctly perform the test.

Specifications and tools:

• 2004 Suzuki 40 horsepower (model 04001F DF40) factory compression ratio: 10:1
• Cylinder compression specifications: 1300 - 1600 kPa (13 - 16 kg / cm2, 185 - 228 pounds per square inch) 
• Cylinder compression maximum difference between any two cylinders: 100kPa (1.0 kg/cm2, 14 psi.)
• Tools required: compression gauge and adaptor, (note: a compression gauge is a diagnostic instrument used for measurement in determining the rate at which squeezing air leaks past piston rings, valve seats, etc.)

Symptoms of low compression:

Outboard motors with low compression are indications of one or more of the following symptoms:

• Faulty seating of valves
• Excessively worn or damaged cylinder wall
• Blown or damaged cylinder head gasket
• Worn or broken piston or piston rings

Testing procedure:

1. Start the 40 HP motor until it reaches normal operating temperatures, then turn off the engine.
2. Detach the port and starboard side motor lower cover.
3. Remove all engine spark plugs.
4. Insert the compression testing gauge into the spark plug’s hole. 
5. Remove the safety lanyard from the motor’s stop switch before cranking the engine. If the lanyard isn’t removed from the emergency stop switch, residual gasoline will enter the cylinder and cause ignition spark from the ignition coil’s discharge. 
6. Remove the throttle levers remote control throttle cable. 
7. Move and hold the throttle lever in wide-open position.
8. While cranking over the Suzuki 40HP outboard engine with the starter motor, note the compression gauge’s max. pressure reading. Then perform the same test procedure to examine each cylinder’s ability at confining combustion pressure. 
9. Upon completing compression on all cylinders, reinstall spark plugs and lower side cover. 

Compression readings typically vary between cylinders. High compression results normally indicate good engine performance. However, always refer to the outboard repair manual specific to the 2004 40HP Suzuki engine when assessing the motor’s condition. Additional testing methods may be included.