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Compression numbers on loop charged engines can really be tricky! Of course you can use the numbers to find a dead cylinder, but hard to prove a good cylinder. Scoring, glazing or just bottle shaped around the numerous ports will misled you as to conditions of the cylinders. Add to that pressure back rings (OMC / not sure what Merc called theirs) and it is hard to determine cylinder condition with just a compression gauge. The main symptom you run into is an engine that will idle for awhile and then fade away and die. You have to choke/prime it to get it to restart. If you catch it while it is slowing down, choking/priming will keep it going. If you pull the head you will fine the cylinder walls scored, glazed or woren at the looper ports (intake). Honing the cylinders will not fix this problem! They require boring oversize with proper honing after boring.
Dan in TN
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