![]() ![]() ![]() Bottom line, if I was buying an older two-cycle outboard I would probably want to see compression values above 75 psi ESPECIALLY if I could not see it run. This sourceseems to confirm with my understanding that 60 psi in older outboards can sometimes be OK. ![]() 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. This source says modern two-stroke outboards should be in the 90 to 105 psi range. 1965 1979 (General Repairs) One thing that I want to convey here is that I write only on motors that I have actually worked on, and over a period of. What I have found unanimously is that the relative compression values between the cylinders should be within 10%. Johnson Johnson, Evinrude, OMC, outboard motor, outboard motor repair, outboard troubleshooting, 6 hp, water pump, carburetor, Maintaining Johnson/Evinrude. Its also rather hard to find where a manufacturer will say the compression range should be from this psi to that psi. For instance, a fully functional Mercury 25 Hp cylinder compression value may be significantly different than that of a Johnson 25 Hp. They not only vary from the reporting individual but from manufacturer to manufacturer. From my research, cylinder compression values that people say are “acceptable” for low horsepower outboards seem to vary. ![]()
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