mercruiser (chevery) 350. Compressions test showed 1 cylinder had 0. All
others were ok. Engine backfires and sputters. Doesn't seem to be leaking
much oil if any at all.

here's what I tried:

--
Pulled the valve cover. Valve is moving up and down.
cranked the motor until the valves were closed, blew compressed air in spark
plug hole, no air came out the exhaust or intake.
yanked the head off, no hole in cylinder (that I can see), head gasket look
ok from what I could tell

Any suggestions?