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Hi a compression check on 1997 2 stroke Yamaha - gave top 70 middle 65 lower 65psi - a little hard to start sometimes but otherwise runs well. What are they supposed to be and what is the likely fix ? worn rings - I am a fairly competent amateur - outboards are not my thing and well aware that a little bit of knowledge is dangerous !
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Seems a bit on the low side.
How was the test done? Should be motor fully warmed up, all plugs removed, throttle wide open and battery fully charged. Crank the motor until the pressure stops rising. Hopefully, the gauge is accurate.
More importantly, how does the motor start, idle and run? -
your gauge is most likely not been met/caled.
your numbers should drop about 5PSI from #1 to #3.
MECHANICAL issues wont create NOR cause SOMETIMES issues.
if it mechanical it either is broke or ok.Comment
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Compression guage
Thanks for the replies - just tried the gauge on my other outboard - 30hp Tohatsu 2 stroke 2006 - 114psi both cylinders. Test cold on both engines - one plug at a time 'neutral' throttle open? Battery fully charged.
Idles OK. A little iffy starting crank 15 seconds, stall, crank 5 seconds OK. Warm no problem 1 second crank. Carb's next step - only tested compression because have bought bigger motor - as kids bigger and do not want to sell anything with a problem.
Roger.Comment
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Rings could be carboned up /stuck.
shock treatment/Heavy doss of ring free or seafoam might help if it is carbonComment
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Would this involve taking the head off? Or Seafoam first - then remove the head?Comment
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do some research on shock treatments with ring free or seafoam
no need to pull the head following their procedures.
But cannot guarantee that will fix it, cause we do not know what the problem really is.
The Yamaha shops have a treatment they use to clean combustion chambers, but us regular people cannot get our hands on it. I think it does the rings alsoComment
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