How much compression should an outboard have?
Good working outboards generally have a compression of 75 to 85 psi. Any readings below 70 psi are considered to be low compression. As a general rule a compression of 135 PSI or better is excellent. Similarly, A compression of 85 PSI or lower is extremely bad.
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 should I expect on a 1999 225 hp Mercury?
I just purchased a 1999 22′ Aquasport with a 1999 225 Mercury Optimax Outboard with 624 hours. I paid for a professional Certified Marine Survey. The Compression test was good on all cylinders and the … read more
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 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?
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.
I just purchased a 1999 22′ Aquasport with a 1999 225 Mercury Optimax Outboard with 624 hours. I paid for a professional Certified Marine Survey. The Compression test was good on all cylinders and the … read more
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?
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.