8hp compression

[gford001]

Quick one.
My mates got a 2004 Johnson 8hp 2 stroke outboard and he was selling it. Someone asked what compression it had.
He is pretty handy, so borrowed a compression gauge, but could only get about 60psi.
The engine was in perfect condition, so he wasn't concerned about it being clapped out (done about an hours work as an auxiliary).
I thought it should be more then that, and he admitted he might have done it wrong.... but out of interest what sort of psi should it have?

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[gazza2006au]

Quick one.
My mates got a 2004 Johnson 8hp 2 stroke outboard and he was selling it. Someone asked what compression it had.
He is pretty handy, so borrowed a compression gauge, but could only get about 60psi.
The engine was in perfect condition, so he wasn't concerned about it being clapped out (done about an hours work as an auxiliary).
I thought it should be more then that, and he admitted he might have done it wrong.... but out of interest what sort of psi should it have?

Sent from my SM-G960F using Ausfish mobile app

You need to disconnect the throttle and open the throttle wide open, remove all spark plugs than do the test it should read about 90psi on that small engine

[gford001]

You need to disconnect the throttle and open the throttle wide open, remove all spark plugs than do the test it should read about 90psi on that small engine

Cheers mate, I'll let him know.

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[Fed]

When a two stroke piston is at the bottom it's completely open to the outside air, throttle opening is an internet myth.

[gazza2006au]

Pretty sure with throttle closed your creating a vacuum between the port and butterfly valve which would suck air back into the crankcase before its locked into the top of cylinder to compress hence u get lower compression readings

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[ericcs]

iv'e had a few 6 and 8hp evinrudes in the last couple of years, and iv'e found that 105psi is about as good as it gets!