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Old 11-12-2021, 04:59 PM
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Jo Ross Jo Ross is offline
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Pressure Drop All Cylinders?

I asked this in a facebook forum and got some interesting answers but want your input:

Any ideas why all four cylinders would drop in pressure when tested cold? Previously had a solid 120 but now all cylinders read right around 60.
I brought the boat out of winter with great success but the other day on a long sail coming out of an inlet it started dying as the boat pitched with the waves. I suspected back pressure since the exhaust was plunged under the water with those waves. Had a few runs where the engine died with little indication of why. Dying when at idle was particularly repeatable. The next morning, the engine had a lot of difficulty starting. Cleaned off some very sooty spark plugs when it sounded like I had a misfire. Compression test of all cylinders and spark test sat but the pressure in all four was about 60psi.
Fuel level was almost full.
Eventually I got her running and got out of the marina confidently on flat water with throttle.
Thoughts?
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