On Wed, 11 May 2005 15:01:56 -0400, Mike G
wrote:

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?

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.

I agree with you, but for a different reason.

My argument is that GPH is a more reliable measure of efficiency
because it covers the spectrum from sitting at the dock warming up to
running full throttle. For example, my Ranger with the 200 FICHT
averages 5 to 6 gallons per hour considering everything. At cruise,
which is about 35 mph, it's about 8 GPH and that seems to be pretty
consistent in most sea conditions. The base is 8 GPH and from there I
can figure MPG - believe this or not, I just typo'd MPH :). So the
way I look at it, GPH is essential to determining MPG and thus the
more relevant factor in determining efficiency.

We argued this for a freakin' hour this morning. :)

Of course, he's a physicist - dumbass. :)

Later,

Tom