View Single Post
  #2   Report Post  
Old April 18th 06, 08:18 PM posted to
Posts: n/a
Default Speed and Fuel Consumption Curve

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

thats some pretty interesting findings, Chuck

My brother wonders why I don't max. out my little 4 cyl. Chris Craft. I
usually run it at 31-3200 RPM Plane speed +. Instead of WFO at

For the wear and tear, and fuel consumption, you really don't gain a
whole lot. The performance doesn't outweigh the benefit of over all