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Old April 19th 06, 03:52 AM posted to
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Default Speed and Fuel Consumption Curve

Jim Donohue wrote:
wrote in message
Just finished a *long* article about a very nice new boat.

Here's an interesting study in fuel efficiency from last Friday's test

50-foot boat, 50,000 pound displacement when fully laden. (We ran the
test light ship),
525 HP single John Deere 6125AFM. 40X 32 prop.

700 rpm. 5.5 knots, 1.4 gph. (better than 3 nmpg)

1050 rpm. 8 knots, 3.5 gph. (still better than 2 nmpg)

1200 rpm. 8.7 knots, 5 gph.

NOTE: Fuel consumption increased roughly 40 percent between 8 knots and
8.7 knots, accomplishing less than a 10% increase in SOG.

1375 rpm. 9 knots, 7.4 gph

Note: Fuel consumption increased roughly 50% to achieve about a 4-5%
increase in SOG

1500 rpm. 10.2 knots, 10 gph (roughly 1 nmpg)

Note: Fuel consuption about 35-40% higher than at 1375 rpm, but better
than a 10% increase in SOG


1700 rpm, 11 knots, 14 gph.

Note: once again about a 40% increase in fuel burn to realize less than
a 10% increase in speed.


2150 rpm, WOT, 14.6 knots, 27 gph,

Note: Almost 100% increase in fuel consumption from a 1700 rpm cruise,
but only about a 33% increase in SOG

Almost a perfect coast boat. You poke along mostly in the low range from
port to port...but when you finally hit the ugly parts you push to the
upper. Says you can basically avoid overnights.

My wife would love it...what does it have for stabs?

This particular vessel wasn't rigged with stabilizers, but the mounting
pads were molded at the factory for easy retrofit. For inland water
usage, or even primary use in the Inside Passage, I would probably take
a "wait and see" attitude for a season or so before adding stabilizers.
For extended offshore coastal cruising, where you often deal with a lot
of beam seas on the west coast, I'd probably add some WESMAR's right

I'll post the review later this evening. It's about 2900 words, so it
will take a while to slog through if you want to know more about the