On Wed, 23 May 2007 13:36:34 -0400, Wayne.B
wrote:

I have a trawler with twin diesels, and running on both engines is the
normal mode of operation for us and others. I like the redundancy but
I'm sure there is a price in fuel economy. It's difficult to say just
how much but probably at least 50% greater. At low engine output
there is a great deal of power wasted just in overcoming friction in
the redundant engine, transmission and running gear.

Either of my engines could easily power the boat at hull speed in
normal conditions. Running single is a possibility but that has other
issues, and you are also dragging around a large unused prop.

I understand the prop drag, but what are the other issues, besides the
obvious higher rpm on the running engine?
The redundancy is a big advantage, and I'm wondering if there is a
sweet spot regarding speed/hull/engines/prop where you can have your
twins and still minimize fuel consumption without paying too much on
the other "issues."

--Vic