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TOPIC: cause of low compression

cause of low compression 2 weeks 17 hours ago #141423

  • 63 Sabre
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Looking at a '77 Evinrude 140hp but has low compression in all four cylinders, 75.80.etc. What would cause this to be in all four?
Maybe running with no mix? Over heat and warped heads?. Can get it really cheap with working tnt. Everything else is good.
Opins please.

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cause of low compression 2 weeks 14 hours ago #141425

OMC never publicized compression. Only that they should be within 10%

Cold engine, no back pressure & large exhaust ports will all cause low compression at cranking speeds. My old 90 DU only reads 60 or so.

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cause of low compression 2 weeks 8 hours ago #141426

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Thanks, Now I'll probably get another motor to hang on the wall. Nothing like having an over powered backup for a 15 footer.

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