Repeating the same thing over and over doesn't make it true. If you go to the
specs for the engine you mentioned, the Yanmar 4JH30-HTE
http://www.mastry.com/products/4jh3hte.htm
You'll find the best "specific fuel consumption" at about 2500 rpm, compared to
a max rpm of around 3600, or peak torque at 2900 rpm. The Fuel usage, in
grams/hp-hours is 153, which corresponds to almost 21 hp/gal-hours.

Now you can make your claims over and over, but the spec sheet simply don't
support them.

I don't know what Donal's original claim was, and I certainly wouldn't trust you
to repeat it faithfully. Although 10 Imperial Gallons seems small, it isn't
outrageously so - I've been on a number of boats with under 20 gallon tanks. My
first keel boat had a six gallon tank.


"JAXAshby" wrote in message
...
jeff, max fuel efficiency on a diesel (as well as a gas) engine is at max
torque rpm. Run the engine above or below that max and fuel efficiency goes
down. On diesel engine *generally* the max torque rpm will be *around* 85% or
so of max hp rpm. On a gas it will *generally* be *around* 70% or so of max
hp
rpm.

in addition, donny's story of the past had him saying he needed the full 10
gallons each way "because he had to get there" or some such, meaning he had a
schedule to keep and he couldn't sail fast enough to "get there" in time.

A *little over* 16 hp per gallon of fuel burned is right where the industry
quotes its fuel consumption rates for water-cooled, 4-cycle diesel engines of
modern design in good to excellent condition.

It wasn't "proof positive," I was simply providing a number given on the
Yanmar
spec sheet. At reduced RPM, the HP at the flywheel is much greater than
what
is produced at the prop.

And there's a huge difference between 16 hp per gallon and 21 hp per gallon.
Improving fuel efficiency over 25% is nothing to sneeze at. I've never
argued
that there isn't a relationship here - only that your number isn't quite
right.

Further your fundamental claim is flawed because Donal's 28 hp engine is
probably run at reduced throttle and actually puts out about 12 hp to cruise
at
80% of hull speed. (I'm just guessing because I don't know the details of
his
boat or engine.) He probably uses slightly over a half gallon to go about 7
miles. Doing that, 10 Imperial Gallons is plenty to get him over to France
and
back.



"JAXAshby" wrote in message
...
jeffies, you are just too stupid to deal with.
yesterday you were claiming you had proof positive that diesels put out
upwards
of thirty hp per gallon in just about any condition, and today you are
quibbling that brand spanking new engines operating under laboratory
conditions
are claimed by their manufacturers to get just over the 16 hp per gallon I
stated as the norm.

now, go quibble that 16 hp is more like 16 point something hp.

Then why do you keep providing sources that have better efficiency? The
Yanmar
you mentioned, according to the Mastry site, is over 20 hp/gal-hours.
Even
your
Indian farm engines were 18 hp/gal-hours. You keep making a claim, than
providing sources that prove you wrong! You certainly seem dumber than
Old
Thom's farts!


"JAXAshby" wrote in message
...
jeffies, give it up. you merely make yourself look a luddite.

modern, water-cooled, 4-cycle, brand spanking new diesel engines in
laboratory
conditions use about 1 gallon of fuel for each 16 hp produced.

Now you're using de-tuned farm engines to prove your point. But once
again,
you
screw it up! On the same page they list others that are over 18
hp/gal-hour,
and that's detuned to run at 1500 rpm, and using US gallons. Those
numbers
listed as "Specific Fuel Consumption" is in "grams per HP-hour"; you
have
to
be
capable of a bit of math to properly convert to hp-hours/gallon.

"JAXAshby" wrote in message
...
old fart, here is the Lister engine under brand new engine, and
laboratory
conditions claiming about 19 hp/gallon/hour (that's Imperial gallons,
btw)

http://www.lovson.com/engineering.html