Sorry, Gould. Bad day. Still, my point is made. The idea is that heat
exchangers are to allow use of the system when the boat is not tied to
shore power.

Perhaps this prevelance is influenced by geography, but I've seen this
type of system on more sailboats than powerboats of comparable size.
These observations support my statement that this setup is more prevelant
in sailboats. Sailboats are more likely to be underway for longer
periods of time and are more likely to be anchoring without ammenities.
Add to that my statement was in response to a powerboater who has never
heard of such a system and it supports my viewpoint...

You point out the obvious that these can be used on powerboats as well.
Your personal observations may disagree with my statement that the system
is more prevelant among sailboats, but your just picking nits.

Bob Dimond