On Sun, 06 Apr 2008 10:30:44 GMT, Jere Lull wrote:

On 2008-04-05 22:14:15 -0400, Bruce in Bangkok said:

On Sun, 06 Apr 2008 00:31:52 GMT, Jere Lull wrote:

On 2008-04-05 09:48:23 -0400, Bruce in Bangkok said:

I suspect, but can't prove that yacht engines are seldom run at maximum
continuous horsepower settings for any length of time while most
commercial engines are.

Talking around the docks, and here, I find that most 'yacht' engines
are also either at idle or 80+% of designed revs.

I'm a bit unusual that I normally power at less than 80% of the
engine's max revs to maximize fuel economy. At 70-75% of max revs, we
get 25-30 mpg. 80% has us pushing against hull speed. Full revs push us
over hull speed, and I've only done that twice in 15 seasons.

Most sailors run at high power when they motor. If they turn the motor
on, they're by definition in a hurry.

Your engine is too big, simple as that :-)

No disagreement, but it was an engine new to the market. Its
predecessor would have been just right, but I liked the idea of the
closed-loop fresh-water cooling.

I still prefer it, truth be told.

By the way, how do you calculate miles per gallon? No tides in the Chesapeake?

We have tides, more accurately we have currents that tend towards a
full knot southbound in our area, but I'm dividing average speed
through the water by average fuel burn. Speed over the ground will vary
with the current of course.

That is a legitimate method although a little depressing at times. I
was coming up the Malacca straits (with too small a prop) and
according to the Knot Log was doing 4 knots. According to the GPS, 1
knot. Not only that but my wife kept saying "when are we getting to
....., Why aren't we going faster...." Not one of my better trips.

Not only that but when I took the too small, full feathering, very
expensive, propeller off and had it for sale at a "second hand" boat
stuff shop the shop got raided by customs who declared the entire
stock as smuggled, i.e., not duty paid and my prop got confiscated.

Not a good experience at all.

Over in the dry (N.E. monsoon) season you motor when there isn't any
wind, which is usually when the land breeze dies about 11:00 every
morning.

Exactly. You're in a hurry. Otherwise, you'd wait for the wind to come back.

;-)

The wind will come back tomorrow, about 08:00, for three hours.

Nothing wrong with that, since that's why we have auxiliaries, but few
sailors power much below hull speed. By dropping the speed a knot or
so, consumption drops dramatically.

If we have the auxiliary on and in gear, we pull nearly 3 knots at
idle. But our most economical speed is about 5 or 5.5 knots. Our
theoretical hull speed is 6.65 knots, though Xan is as comfortable at
7+ knots as 5 under sail.

Come to think about it, she's more comfortable above that speed than
below, but she is a known show-off that delights in breaking the rules.
She considers hull speed a suggestion, not a law.

Do you sail with only your wife ( or significant other) or do you
have a mob aboard? I have a 40 ft. sloop and find it a fine boat for
myself and my wife but a bit small for more. Or perhaps I'm a just a
grouchy old man.

The last passenger I had aboard was a friend of a friend that had
helped the friend to bring his boat back to Thailand when the friend
was sick. As a result he didn't have the correct stamps in his
passport and I was asked to take him back to Malaysia. .

I picked the guy up at a remote island and he obviously had been
drinking beer for the better part of the day and hadn't bothered to
bathe in the past few days. As soon as he came aboard I explained that
we slept on the deck as it was too hot down below and even then my
wife birched (in Thai) for the two days we had him aboard. No more
favors for that "friend".

Bruce-in-Bangkok
(correct email address for reply)