The number I've used for marine engines is 0.055 Gallons per HP per
hour. For gas engines, use 0.1.


Brian Whatcott wrote:
Here's the scoop on fuel efficiency. It's an engine parameter called
specific fuel consumption. The most efficient aero recips use
0.45 lb per HP hour.

A diesel could be 50% more fuel efficient, let's say.
So 0.3 lb diesel fuel per HP.hr would need 26 lb fuel per hour
to produce 85HP
That's 4 gallons or more....for 84HP

I guess this means Doug is using full revs at 1/4 throttle,
or full throttle at 1/4 max revs....

Regards

Brian Whatcott Altus OK

On Wed, 23 Feb 2005 20:41:51 -0500, "Doug Dotson"
dougdotson@NOSPAMcablespeedNOSPAMcom wrote:


Something must be wrong with your figures or your engine/prop
situation. I run a 1985 Perkins 85 HP 4 cylinder pushing a 43'
boat. I consistantly burn 1 GPH.

Doug
s/v Callista

wrote in message
roups.com...

Another thread discusses sailboats motoring "too much" but I think most
sailboats will use their engines to supplement sail but we still worry
about fuel economy. Even motoring alone, my yanmar 2GM seems to burn
only about 1-1.5 gals/hr at 6 kts in my 28' S2 but still I wonder about
the best way to conserve fuel in very light air.
Normally, in light air, I start with sails and no engine and eventually
get impatient with going only 3 kts and start the engine and put us up
to 5 and then eventually 6 kts or more. It is this last little bit
that I think burns the most fuel because she is most efficient at
slower speeds but as we get closer to hull speed fuel use rises
sharply.
An alternative strategy that would burn less fuel but would go a little
slower might to be ALWAYS run the engine at sufficient rpm to get to
3.5 kts and then use the sails to supplement that.