[OMC-Boats] Loss of compression and stalling question

I was boating on Lake Powell over the last 5 days and had the following problem:

Intermittently slows then ultimately stalls when over 1.5K RPM for any duration over 1 min
  a.. I found a loss of vacuum where the carburetor meets the manifold and successfully addressed via using gasket sealer...yet, still experienced the following
  b.. Running low compression no matter what tweaks made to carburetor pins and idle RPM setting (14 at best ; usually 15 - 16...maybe this is attributable to altitude?)
  c.. Compression = ~7 - 10 at 2K RPMs
  d.. Compression = 5 at 2.5 - 3K RPM
Could be loss of compression elsewhere, timing, or other? Any thoughts and recommendations would be appreciated.

Thanks,
John
'67 Surfer
Received on Tuesday, 22 June 2010