99 200 Mercury EFI same low compression all cylinders?

Joined
Mar 31, 2010
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11
I replaced some faulty head gaskets a few months ago and then ran a compression test which tested 112 - 115 psi on all cylinders. It worked great for a while. Gradually , the motor slipped back to the way it was acting before. Checked the compression today and found 60 - 65 psi all cylinders. I took the heads back off and could not find any visible problems. Anyone know what i should do?
 
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