On 2007-12-09 13:14:12 -0500, Wayne.B said:

On Sun, 09 Dec 2007 17:41:37 GMT, Jere Lull wrote:

In particular, check the difference in fuel usage at the same cruising
speeds, as I've found it's easy to set the same RPMs, benefit from
increased speeds, but suffer from decreased mileage.

Since it inevitably takes more net horsepower to increase speed,
increased fuel usage should be expected. There's no free lunch... :-)

Well, it *feels* like a free lunch when the same fuel burn results in
higher speeds or there's less fuel burned at the same speeds due to a
more efficient prop.

When we got Xan's then-new engine, we were told to expect a 1 gph burn
because that's what the original transmissions and props gave. With our
higher gearing and larger prop, we burn only a quarter or third of that
at about the same speeds. That the difference in efficiency between a
dinky 12x8 spinning at 2500 rpms or more, and a 16x10 spinning at about
1200.

The switch from old 3-blade to modern 2-blade won't be quite as
dramatic, but I expect there will be some improvement, though it seems
he doesn't have a tach for reference.

--
Jere Lull
Tanzer 28 #4 out of Tolchester, MD
Xan's pages: http://web.mac.com/jerelull/iWeb/Xan/
Our BVI trips & tips: http://homepage.mac.com/jerelull/BVI/