How to Compression Test an Outboard Engine | BoatUS

Learn how to perform an outboard compression test to evaluate engine health and avoid expensive repairs on your next boat.

Buying a used boat requires knowing exactly how much life remains in the engine. Yamaha technician Sean Stahl explains that an outboard compression test is the most effective way to gauge the condition of the pistons and rings, revealing how well the engine functions as an air pump.

Whether you are performing routine outboard motor maintenance or inspecting a potential engine, you need to know how to use a compression gauge properly. We will show you how to read the PSI across each cylinder and interpret the results to ensure your engine is within the acceptable 10% variance.

Subscribe for more essential boat care tips, and tell us in the comments if you have ever discovered a major engine issue during an inspection.

📗CHAPTERS
0:00 Introduction to compression testing an outboard motor
0:20 Why do a compression test on an outboard?
0:37 What do you look for when performing a compression test on an outboard?
1:07 How to perform an outboard compression test
1:57 Why pull the spark plugs when performing an outboard compression test?
2:17 How do you keep fuel from flowing and the engine from firing when performing an outboard compression test?
2:48 What is a compression gauge and how do you read it?
3:06 How do you attach a compression gauge to an outboard
4:00 What do outboard compression test readings mean?
4:22 Conclusion to compression testing an outboard

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