On Sun, 25 Nov 2007 10:23:55 +0700, Bruce in Bangkok
wrote:

Have there been any studies made of shutting down one engine? I know
that Beebe published some RPM/Miles/fuel consumption charts but those
were for a single screw drive.

I don't know if I'd call it a study, but based on my own statistics
there is a definite save, even with the drag of a freewheeling prop.
My situation may be different than some however since the engines are
oversized for 95% of my typical usage. As a result, running both
engines slowly is not only bad for them, but they would be operating
just above idle speed which is not an efficient operating point.

By running on a single engine, it is operating closer to it's design
point which is not only more efficient but minimizes potential
maintenance issues like carbonized valves, rings and exhaust manifold.

My statistics for RPM vs fuel burn vs horsepower vs speed agree fairly
closely with Beebe's numbers. Of course there is a fudge factor in
his equation which is different for every hull shape. It turns out
that the Grand Banks hull form is at the low end of the efficiency
scale.