I had a debate with a friend this morning concerning miles vs gallons
per hour.

I contend that gallons per hour is a more reliable method of
determining how far and fast a boat can/should go. Obviously, my
friend took the opposite viewpoint.

What is the collective wisdom concerning these measure of fuel
efficiency?

Later,

Tom

"Shortwave Sportfishing" wrote in message
...
I had a debate with a friend this morning concerning miles vs gallons
per hour.

I contend that gallons per hour is a more reliable method of
determining how far and fast a boat can/should go. Obviously, my
friend took the opposite viewpoint.

What is the collective wisdom concerning these measure of fuel
efficiency?

Later,

Tom

Depends on the boat. Trawlers, etc gallons per hour, but performance boats
that run at difference speeds, average miles per gallon seems better.

"Shortwave Sportfishing" wrote in message
...
I had a debate with a friend this morning concerning miles vs gallons
per hour.

I contend that gallons per hour is a more reliable method of
determining how far and fast a boat can/should go. Obviously, my
friend took the opposite viewpoint.

What is the collective wisdom concerning these measure of fuel
efficiency?

Later,

Tom

First of all, miles per hour is totally unrelated to fuel efficiency. It is
simply speed. A 19 foot ski boat and a 65 foot sports fisherman can both go
40 mph with vastly different efficiencies.

Gallons per hour is only indirectly related to efficiciency. You can sit
idling at the dock and use a certain number of gallons per hour - and your
efficiency is zero.

Efficiency is miles per gallon. If you know your speed then gallons per hour
can be converted to miles per gallon. Likewise if you know your gallons per
hour then speed can also be converted to miles per gallon.

Knowing how far a boat can go is related to miles per gallon and fuel tank
capacity.

Basically you were both wrong!

--
Peter Aitken

"Shortwave Sportfishing" wrote in message
...
I had a debate with a friend this morning concerning miles vs gallons
per hour.

These two items are different than the ones listed in the header. The text
above quotes MPH vs. GPH. The header quotes GPH vs. MPG. I'm sure you
realize the MPH and MPG are entirely different calculations, but perhaps
your end of the debate would be strengthened by consistency. Given the
discrepancy, I'm not sure if you are arguing GPH vs. MPH or GPH vs. MPG.
Either way, I'm not sure I understand the basis for the debate altogether,
as each tells a different thing, presumably to be used for different
purposes. GPH will tell you fuel consumption over a fixed period of time,
but as it has no accounting for speed, it has no direct accounting for
distance traveled in that period of time, so by itself is not reasonable
measurement of fuel consumption over distance traveled. MPH is simply a
measurement of speed, with no accounting for fuel consumption at all. MPG
is perhaps the more useful measurement of the three, because it calculates
fuel consumption for a given distance traveled, but may not be as relevant
as GPH for some.



I contend that gallons per hour is a more reliable method of
determining how far and fast a boat can/should go. Obviously, my
friend took the opposite viewpoint.

What is the collective wisdom concerning these measure of fuel
efficiency?



Which of these is more appropriate for you will depend much on your boat and
the way you use it. For instance, if your boat is a trawler type, without a
great variation of speed, or if the majority of your engine hours are at
idle or trolling speeds, it may be that GPH is the most relevant measurement
of fuel consumption. for you. On the other hand, if your boat has
significant variations in speed, and is used to travel large distances, MPG
would more likely be the consumption measurement of choice.

My own case offers an interesting study. I have a 29' twin gas I/O cruiser,
with a top speed of 41 MPH, a typical cruise speed of 30 MPH, and I also
spend a significant amount of time gunkholing at idle and leisuring cruising
at about 8 MPH. Whenever I buy fuel, I always fill the tank completely, and
maintain a detailed fuel log with engine hours since last fill, gallons
used, and distance traveled. Distance traveled is generated from the GPS,
which has a resetable odometer function, which I reset at every fueling.
The boat never moves without the GPS being turned on and therefore recording
accumulated distance traveled.

Depending on how the boat was used for that particular tank of fuel, my GPH
will fluctuate dramatically. My fuel log (going back 5+ years) shows a GPH
high of 18 and a low of 3.6. Quite a range. I have two entries showing
18.0 GPH, with both of them being non-stop long distance cruises, using the
logged fuel in a matter of hours. One was a run of 133 miles using 109
gallons, and the other was a run of 67 miles using 49 gallons. I was at a
high speed cruise the entire time on both runs. At the other end of the
range, the 3.6 GPH entry logged 141 miles using 102 gallons, but over a four
month period of time. This was a period of time where the boat never really
went very far at any one period of time, and consisted of mixed usage at
high cruise speed and quite a bit of gunkholing at low speed cruising. I
also have many log entries with GPH readings anywhere between the 3.6 and
18.0 GPH readings. So for me, GPH isn't a very meaningful statistic by
itself.

On the other hand, and I've always found this somewhat fascinating, even
with GPH readings all over the place, my MPG readings are remarkably
consistent. MY MPG high and low readings are 1.41 and 1.22, with the vast
majority of them hugging around 1.3 MPG. For instance, the 18.0 GPH
readings resulted in 1.22 and 1.38 MPG readings. The 3.6 GPH reading
resulted in a 1.39 MPG reading. What this tells me is that my boat gets
about 1.30 MPG whether I'm cruising at 3500 RPM and 30 MPH or at 1700 RPM
and 8 MPH. Obviously the former has a much higher GPH reading than the
latter, but the MPG readings seem to equalize. I would have never guessed
that both those speed would offer the same MPG, but it has been offered up
way to many times to be denied.

So for me, GPH is pretty much irrelevant, while MPG is highly relevant. If
my MPG readings started to consistently show less than 1.2, I would start to
suspect something amiss with one of the engines. GPH readings would give me
no such clue. So I guess that puts me on the other guy's side of the
debate. But, as they say, your mileage may vary.

RG

In article ,
says...
I had a debate with a friend this morning concerning miles vs gallons
per hour.

I contend that gallons per hour is a more reliable method of
determining how far and fast a boat can/should go. Obviously, my
friend took the opposite viewpoint.

What is the collective wisdom concerning these measure of fuel
efficiency?

Later,

Tom


Actually, as stated I'd have to opine the gallons per hour was almost
right or rather only part of that side of the argument.

I'd would think gallons per hour at X rpm is much more accurate for a
boat. With all the variable forces acting on a boat in motion, hull and
upper works design, wind, or current, for example

A boat at, say, 3500 RPM isn't going to cover the same distance with a
head wind and cross current as a boat with a tail wind and following sea
or one in a dead calm and glass smooth surface. The only constant you
can really use to figure your range at any specific time is the is the
fuel consumption at that RPM rate.

Let's say your favorite fishing grounds is, under ideal conditions, a
two hour run at the boats ideal cursing speed/RPM. That makes things
easy but how often are you going to find ideal conditions that will
allow you to run at your best cruising speed/RPM with no external
variables to figure in. Once you get past the break water the whole
thing is a crap shoot till you get your RPM's up to where you are
getting the best ride. That may or may not be at your ideal cruising
speed, may or may not be covering distance over the ground at the same
speed as you would in ideal conditions. Again, the constant, RPM.

Hell you can't accurately tell what one automobile will really give you
in miles per gallon. It all depends on how much of a lead foot the
driver is, traffic and weather conditions. You take an EPA rating on a
new car and some people are going to be able to better it some not even
get close. That's why they call them estimates and your mileage may
vary.

--
Mike G.
Heirloom Woods

www.heirloom-woods.net

On Wed, 11 May 2005 16:50:28 GMT, Shortwave Sportfishing
wrote:

I had a debate with a friend this morning concerning miles vs gallons
per hour.

I contend that gallons per hour is a more reliable method of
determining how far and fast a boat can/should go. Obviously, my
friend took the opposite viewpoint.

What is the collective wisdom concerning these measure of fuel
efficiency?

Later,

Tom

If they're both accurate, then they're both reliable. Most of my boating is
cruising to get to the fishing area and then trolling for however long I'm going
to do it, and then cruising back. I figure 8gph cruising and 2 gph trolling.
This morning I cruised about an hour, total, and trolled for about an hour.
(Took that long to catch a 38"er and a 36"er.) So, I figured I burned about 10
gallons, or $25 worth of gas. We split the gas amount.

I'd say the most reliable way is to use a flow meter, but I haven't put mine in
yet.
--
John H

"All decisions are the result of binary thinking."

We've got to assume you're talking about your header subject GPH vs MPG
- not miles per hour as you probably mis-typed above.

GPH is irrelevant, even with a trawler, hull speed type boat (of course
in mho). What does it tell you? How many hours of fuel you've burned,
how many hours you might have left? You'll still need to know how fast
you have gone or expect to go to determine where you can get to with
the fuel you have.

The ONLY reason I can guess that GPH is even used is that it has been
the only thing that could be measured with a normally available,
affordable gauge up til now. Fuel flow meters are common technology and
have been in use for ages. They can only tell GPH and that is why
people have been using that measurement. Everyone I've boated with
whether in a planing hull or displacement hull has a GPH flow meter,
but uses that info to mentally convert to MPG using their GPS or
speedometer reading. Yes, if the boat is a pretty steady traveler,
they could short cut by just looking at GPH, but when push comes to
shove (e.g., can we make it "there"), it is MPG which will tell you
what you need to know.

My only reason to have a flow meter on my boat (GPH) is to ultimately -
through a mental calculation- determine the most efficient speed, in
other words, the speed that maximizes MPG.

Nowadays, it becoming more common have the flowmeter GPH input to the
GPS's MPH measurement to give you an MPG reading on your GPS screen.
If I could afford a new unit, I would definitely get that feature -
because again, that's the only reason to measure GPH in the first place.

Gene Kearns wrote:
..

For example, a boat traveling into a 15 mph current at 15 mph could
be
expected to get 0 miles per gallon, but would reasonably be expected
to burn Y gallons per hour developing the requisite horsepower to
maintain 15 mph....

So, Tom, I'm with you on this one, since we are traveling in a
movable
liquid and at the mercy of the wind. Get a totalizer... at least
you'll know where you stand and how far off shore you are likely to
run out of fuel....

--

You need to measure your speed with something accurate like a GPS - I
do rivers all the time (90% of my boating). I don't know anyone who
would have the error you're talking about, if they use a GPS for speed.

Both terms can be useful, especially for planning purposes, and when
used together.
If you have an engine with known GPH at specific rpm's (+/- a small
percentage) you can easily plan ahead for consumption and reserves for a
specific distance at various speeds or for days of operation (where
mileage isn't a consideration) before needing to "watch for a gas station".
Although MPG/MPH is great for planning, it doesn't take into
consideration that it's "through the water", so that even when connected
to a GPS, the number will vary up and down.
In the end, a lot depends on type of boat, type of operation, and route
to be traveled.
To be honest, I'd use both for comparison. Most ships use B/M
(barrel/mi) with a reserve of 2-3 days .... always calculate some degree
of reserve.

otn

On Wed, 11 May 2005 11:45:11 -0700, "RG" wrote:


"Shortwave Sportfishing" wrote in message
.. .
I had a debate with a friend this morning concerning miles vs gallons
per hour.

These two items are different than the ones listed in the header. The text
above quotes MPH vs. GPH. The header quotes GPH vs. MPG. I'm sure you
realize the MPH and MPG are entirely different calculations, but perhaps
your end of the debate would be strengthened by consistency. Given the
discrepancy, I'm not sure if you are arguing GPH vs. MPH or GPH vs. MPG.
Either way, I'm not sure I understand the basis for the debate altogether,
as each tells a different thing, presumably to be used for different
purposes. GPH will tell you fuel consumption over a fixed period of time,
but as it has no accounting for speed, it has no direct accounting for
distance traveled in that period of time, so by itself is not reasonable
measurement of fuel consumption over distance traveled. MPH is simply a
measurement of speed, with no accounting for fuel consumption at all. MPG
is perhaps the more useful measurement of the three, because it calculates
fuel consumption for a given distance traveled, but may not be as relevant
as GPH for some.

So I take it you have never made a typo in your entire life?

Damn, it must hard to be so perfect. :)

I contend that gallons per hour is a more reliable method of
determining how far and fast a boat can/should go. Obviously, my
friend took the opposite viewpoint.

What is the collective wisdom concerning these measure of fuel
efficiency?

~~ mucho snippage ~~

So for me, GPH is pretty much irrelevant, while MPG is highly relevant. If
my MPG readings started to consistently show less than 1.2, I would start to
suspect something amiss with one of the engines. GPH readings would give me
no such clue. So I guess that puts me on the other guy's side of the
debate. But, as they say, your mileage may vary.

Thanks for your input.

Later,

Tom