How do these piston walls look...

Discussion in 'Outboard Maintenance' started by Dillusion, Dec 21, 2012.

  1. Dillusion

    Dillusion devilray snob

    Top piston compression 65, lower piston compression 125 with throttle in start position, not wot.

    Here's some photos of my pistons from the exhaust manifold ports as well as the top side check port on the other side of the outboard:

    Anyone see any problems? All I can see is some scoring on the top piston sidewall...culprit for the low compression?

    Top Piston/Cyl:

    Top Piston Rings Side 1 -

    [​IMG]

    Top Piston Cylinder Wall Side 1 -

    [​IMG]

    Top Pistol other side Check Port -

    [​IMG]

    Top Piston Rings other side Check port -

    [​IMG]



    Bottom Piston/Cyl:

    Bottom Piston Rings Side 1 -

    [​IMG]

    Bottom Pistol Cylinder Wall Side 1 -

    [​IMG]
     
  2. AfterHours2

    AfterHours2 Stripper in my own Mind!

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    At 65 psi, you have an issue that is probably not noticable with the piston still installed. Did you do a comp test when you bought the motor? It looks like its time for a tear down that way you can see what caused the low compression. But yes, the scoring is one of the reasons for the low compression..
     

  3. Creek Runner

    Creek Runner Well-Known Member

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    2nd picture scoring looks bad, and no way that motor hasn't been ringed before.
     
  4. Dillusion

    Dillusion devilray snob

    By that you mean that someone has already re-bored or honed it? Or just replaced the rings?
     
  5. Creek Runner

    Creek Runner Well-Known Member

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    Just mean there is no signs of carbon, which either means it has very very few hours, or someone has been inside before.

    Only way to find out is to break it down and see if theyare STD pistons, and even then they could have honed and replace the rings.