I lost the posting, but someone has asked me for the measurements of
my Fluidyne oil/water heat exchanger that I'm using on my 20B.
Finally, today I remembered to take the measurements.  Keep in mind
that they do not include the mounting brackets or fittings, but just
the basic box.  The Length is 15", Height is 6-1/4", and Width is
4-1/2".

Mark S.