What is good compression on a Mercury outboard?
What Outboard Compression Test Results Mean. Results vary depending on whether the outboard is a Four-Stroke or a Two-Stroke. Good results for Four-Strokes should be 180-210 PSI, and Two-Strokes should be around 110-130 PSI. Here is everything that you need to know about outboard compression tests.
What should the compression be on a outboard motor?
Good working outboards generally have a compression of 75 to 85 psi. Any readings below 70 psi are considered to be low compression.
What should the cylinder compression be on a Mercury outboard?
From my research, cylinder compression values that people say are “acceptable” for low horsepower outboards seem to vary. They not only vary from the reporting individual but from manufacturer to manufacturer. For instance, a fully functional Mercury 25 Hp cylinder compression value may be significantly different than that of a Johnson 25 Hp.
What causes a bad compression test on a Mercury 2 stroke?
Even a small leak will result in a poorly performing powerhead as the fuel mixture will become lean causing the temperatures of the cylinder to increase. Lean air and fuel conditions increase cylinder temperatures beyond factory specifications.
What do I need for cylinder compression test?
Its highly recommended to always use a outboard repair manual for your specific year and model outboard engine when preforming a cylinder compression test on your motor. Important information, including correct service procedures, specifications, pictures, illustrations and safety precautions may be included.
What should the PSI be on an outboard compression test?
Results vary depending on whether the outboard is a Four-Stroke or a Two-Stroke. Good results for Four-Strokes should be 180-210 PSI, and Two-Strokes should be around 110-130 PSI. Here is everything that you need to know about outboard compression tests. How to do them and what the results mean for you! What Is A Compression Test?
What’s the compression range on a Mercury 25 HP cylinder?
They not only vary from the reporting individual but from manufacturer to manufacturer. For instance, a fully functional Mercury 25 Hp cylinder compression value may be significantly different than that of a Johnson 25 Hp. Its also rather hard to find where a manufacturer will say the compression range should be from this psi to that psi.
How to do compression test on Mercury 2 stroke outboard engine?
Use rubber of silicone gasket making compounds to provide proper sealing of the plates. 1. Start by installing the adapter plates over the exhaust ports and the intake ports to provide a complete seal of the powerhead. You must make sure that you do not cover the water jacket holes. 2.
What should the compression be on an outboard?
This source says modern two-stroke outboards should be in the 90 to 105 psi range. However if you watch the end my video below you will see that my 1979 Evinrude 6 Hp cranks easily cold (2 pulls) with 60 psi compression This source says the older two stroke outboards below 25 Hp should be between 75 and 85 psi.
What should my compression reading be on my engine?
Compression test results will vary depending on what kind of engine you are working on. Mainly, there is a big difference between Two-Strokes and Four-Strokes. As we stated earlier at the beginning of this article. Two-Stroke engines should have a compression reading of around 110-130 PSI.