What is 'cruise speed' ?
 

You often see the 'cruise speed' mentioned in boat descriptions and brochures.
But what is this speed and how is it determined?

ZanderU wrote:
You often see the 'cruise speed' mentioned in boat descriptions and brochures.
But what is this speed and how is it determined?


My recollection is that BOATING magazine's "cruise speed" for planing
boats is the throttle setting that produces the best fuel economy while
the boat is on plane. Typically, it is somewhere around 70-75% of the
engine's top RPM on a boat with a gas engine.




--
We today have a president of the United States who looks like he is the
son of Howdy Doody or Alfred E. Newman, who isn't smarter than either of
them, who is arrogant about his ignorance, who is reckless and
incompetent, and whose backers are turning the United States into a pariah.

What, me worry?

My recollection is that BOATING magazine's "cruise speed" for planing
boats is the throttle setting that produces the best fuel economy while
the boat is on plane. Typically, it is somewhere around 70-75% of the
engine's top RPM on a boat with a gas engine.

Actually that would not be correct. The greatest fuel economy with a planing
hull boat (eliminating the "dead idle" option) is achieved just after the boat
reaches plane.

Cruise speed is more RPM related. A speed where you do not stress the engine as
much as running WOT, but still achieve a reasonable speed. I like to say it's
the maximum speed that can be sustained for long periods without unduly
stressing the machinery. It's also a speed where engine temp
remains under control. Some if it is personal preference and there is no
"official" cruise speed for most planing hull boats- but I agree with Harry
that many boaters will "cruise" at 70 -80 % of WOT.

Gould 0738 wrote:
My recollection is that BOATING magazine's "cruise speed" for planing
boats is the throttle setting that produces the best fuel economy while
the boat is on plane. Typically, it is somewhere around 70-75% of the
engine's top RPM on a boat with a gas engine.

Actually that would not be correct. The greatest fuel economy with a planing
hull boat (eliminating the "dead idle" option) is achieved just after the boat
reaches plane.

Cruise speed is more RPM related. A speed where you do not stress the engine as
much as running WOT, but still achieve a reasonable speed. I like to say it's
the maximum speed that can be sustained for long periods without unduly
stressing the machinery. It's also a speed where engine temp
remains under control. Some if it is personal preference and there is no
"official" cruise speed for most planing hull boats- but I agree with Harry
that many boaters will "cruise" at 70 -80 % of WOT.


Hmmmmm.

My fuel flow gauge can beat up yours!

Seriously, my experience more closely matches BOATING mag's.



--
We today have a president of the United States who looks like he is the
son of Howdy Doody or Alfred E. Newman, who isn't smarter than either of
them, who is arrogant about his ignorance, who is reckless and
incompetent, and whose backers are turning the United States into a pariah.

What, me worry?

Gould 0738 wrote:
Seriously, my experience more closely matches BOATING mag's.

It will vary from hull to hull, but if you're just breaking plane at 70-75%
throttle, you need to lighten ship. :-)


The Parker planes in the 16-17 mph range, but if the conditions warrant,
I typically "cruise" the boat at 25-30 mph. The engine seems to have a
wide "cruise groove" range between 4000 and 4500 rpm, but will redline
at 6000 rpm. Actually, I watch the flow gauge more closely..I try to
cruise at no more than 10.1 gph, which corresponds to 4000-4500 rpm. WOT
produces 39.9999999999999999999999999999999 mph. The same boat with a
250 hp Yamaha produces about 42 mph, and with a 300 hp, 44-45 mph. But
to run at those speeds, you need to be an oil sheik.

If I am "driving" from the cockpit, I might run a tad faster, but up
forward (way forward) in the cabin, the ride is bumpier over the chop.


--
We today have a president of the United States who looks like he is the
son of Howdy Doody or Alfred E. Newman, who isn't smarter than either of
them, who is arrogant about his ignorance, who is reckless and
incompetent, and whose backers are turning the United States into a pariah.

What, me worry?

The Parker planes in the 16-17 mph range, but if the conditions warrant,
I typically "cruise" the boat at 25-30 mph. The engine seems to have a
wide "cruise groove" range

Your Parker gets better fuel economy at 25-30 mph than on plane at 16-17?

Very unusual, indeed. I'll have to see if there are some test results that show
others have had a similar experience in the same boat. Could it be that trim or
something is unnaturally and seriously *reducing* your Parkers nmpg at the
slower velocity?

Gould 0738 wrote:
The Parker planes in the 16-17 mph range, but if the conditions warrant,
I typically "cruise" the boat at 25-30 mph. The engine seems to have a
wide "cruise groove" range

Your Parker gets better fuel economy at 25-30 mph than on plane at 16-17?



Very unusual, indeed. I'll have to see if there are some test results that show
others have had a similar experience in the same boat. Could it be that trim or
something is unnaturally and seriously *reducing* your Parkers nmpg at the
slower velocity?


I'll take some notes, but, yes, I'm pretty sure I'm getting more mpgs at
the higher rpms.

My car has a fuel flow gauge, too. I get better mpgs at 60 than at
50...according to the gauge.


--
We today have a president of the United States who looks like he is the
son of Howdy Doody or Alfred E. Newman, who isn't smarter than either of
them, who is arrogant about his ignorance, who is reckless and
incompetent, and whose backers are turning the United States into a pariah.

What, me worry?

Gould,
I thought you got better gas mileage in gallons per hour right after a
planning hull gets on plane, but you got better gallons per mile at
"cruising speed". I was wrong.

I checked out the actually gas consumption used in boat tests and it appears
that while the gallons per mile varies from boat to boat some being better
at planning speed, some better slightly higher than planning speed, and some
are actually higher at 4000 rpm, with Cruising Speed being 3000 rpm.

So it would appear that Gould's statement cruising speed is based upon the
highest RPM that will not stress the engine is correct, but their are some
boats that actually got better MPG at higher than cruising speed.


"Gould 0738" wrote in message
...
The Parker planes in the 16-17 mph range, but if the conditions warrant,
I typically "cruise" the boat at 25-30 mph. The engine seems to have a
wide "cruise groove" range

Your Parker gets better fuel economy at 25-30 mph than on plane at 16-17?

Very unusual, indeed. I'll have to see if there are some test results that
show
others have had a similar experience in the same boat. Could it be that
trim or
something is unnaturally and seriously *reducing* your Parkers nmpg at the
slower velocity?

On 24 Sep 2004 06:47:00 -0700, (ZanderU) wrote:

You often see the 'cruise speed' mentioned in boat descriptions and brochures.
But what is this speed and how is it determined?

Depends on if you are running a displacement hull or a planing hull.
Also depends on engine horsepower, engine type (diesel,gas, two/four
stroke, etc.), dry/wet weights, wind/wave conditions, etc.

There really isn't a blanket answer, but the easiest way to describe
cruise speed is the fastest speed at which the engine is at it's most
efficient. On some boats, it can be WOT. On some, 2/3 throttle. On
my Ranger, it's about 4000 RPM (5600 max) @ 30 mph @ 4.3 Gph. On the
Contender, it's 4800 RPM (5800 max) @ 44 mph @ 5.7 Gph per engine.

Take care.

Tom

"The beatings will stop when morale improves."
E. Teach, 1717

On Friday 24 September 2004 2:47 pm in rec.boats ZanderU wrote:

You often see the 'cruise speed' mentioned in boat descriptions and
brochures. But what is this speed and how is it determined?

The number is determined mainly by marketing issues.

In general it is the speed at which the boat was designed
to operate in a continuous cruise with reasonable comfort
and fuel economy. The tank range is usually specified at
this speed. The word "reasonable" here is rather subjective
and will be interpreted by the brochure writers according
to the market they are targeting and/or competitor figures.

In some cases, such as CAT engines, the engine manufacturer
specifies a maximum continuous power and a higher 30 minute
intermittent rating. This may constrain cruising speed on
some boats.

You can go faster, for example to punch a tide, but the
ride will probably get rough and you will use a lot of fuel.

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