"Wayne.B" wrote in message
...
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.

This has got Dad and I talking about possibilities. He cruises on a GB42 &
I on my Gulfstar 41 Sloop. We've been trying to slow his boat down enough
so I can keep up on a regular basis. I was thinking of buying a small fleet
of large dingies to tow behind him to slow him down, but that's an expensive
option. Sounds like your idea may be well worth experimenting with. The
primary concern for me, would be damage to the transmission....those puppies
are expensive. Maybe this'll help Dad cut down on his fuel bill. I
constantly tease him 'bout it...he normally burns 4.5gph while I about
2/3gph....when I'm motoring. I sure like his GB though...maybe when I get
tired of sailing (whenever that could be). :-)

Glenn.
s/v Seawing.