I haven't done a compression test on it. It puts out full power as far
as I can see -- its a catamaran and the identical engine on the other
w/identical prop doesn't do any better power wise at WOT. Have this
vague idea that it might be a tiny leak in the water jacket but there
is no obvious steam and it doesn't blow water out of the reservoir. It
has about 1200 hours. We cruise in the South Pacific full time so we
take awful fuel and often run the tanks pretty low on passages.
However, the fuel that is in there now is New Zealand fuel and I took
it all out and ran it through a double filter set-up so I'm thinking
its pretty dry...

In my search for leaks I have pulled the engine out and painted it and
cleaned the bilge to surgical standards. I'm pretty sure that no
significant fuel leaks into the boat... If we're leaking into the
crank oil it isn't raising the level noticeablely...

Many thanks to all for the thoughts -- I'm looking at each carefully
and even running the engine as I type.

-- Tom.