On Tue, 20 Nov 2007 04:02:00 GMT, "Glenn \(s/v Seawing\)"
wrote:

Fogive my ignorance. Your GB...works okay to shut down an engine and run on
a single engine, rather than throttle back both? Does the drag of the
stationary prop still make it worth it?

Good question. If you throttle back both engines to run at or below 7
knots, they end up running barely above idle speed which is bad for
them over an extended time. By running a single engine you can keep
it at an RPM range where it is developing a half way decent amount of
power. I still rev it up once in a while for 10 minutes or so.

The other issue with single engine is wear and tear on the
freewheeling transmission. The trannys depend on the engine running
for cooling and lubrication. The manufacturer says that it is OK to
let them freewheel at slow speeds but recommends starting the engine
every two hours for a few minutes.

Economy improves mostly as a result of slower speed. Once you get
above 1 x SQRT(LWL) increased speed results in exponentially higher
hull drag as more energy goes into the wake.