Richard Casady wrote:
On Fri, 4 Jul 2008 06:29:26 -0400, "Jim" wrote:

"Graham" wrote in message
news:ypjbk.54744$Jx.31786@pd7urf1no...
Does anyone know if these gauges display miles per gallon (or litres per
km) or just miles travelled and gallons consumed?

Do they need any special interface to work with standard GPS's like a
Raytheon chart plotter?

Thanks, Graham
The GPS reports miles per hour over land. It would be useless to use those
calculations in determining real miles per gallon over the surface of the
water.

It reports MPH everywhere equally well. It doesn't know sea from land
unless you get it wet. It reports speed over the land and if the land
is flooded, at sea or on a river, there may be an effect from
currents.

Casady


I keep my eye on the water, not on the gauges, unless I'm heading into
shallows, and then I watch out for diminishing depth. If I were
"voyaging" over more complicated waters than Chesapeake Bay, I'd pay
more attention to the electronics, I suppose, but I know the land sights
on both sides from Baltimore down to the mouth of the Potomac, so on a
reasonably clear day, I know where I am in space. This is no great
accomplishment...anyone who pays attention while out on the boat around
here can do the same.

Thanks for the rapid information Vic and to all the others who have posted
interesting comments here

The gps input helps measure the actual speed made good over the ground which
is needed for calculation of best speed for fuel consumption in litres/km
relative to the ground which is what I'm interested in (ie starting and
ending points of my trips are attached to the earth!)

Graham

"Vic Smith" wrote in message
...
On Fri, 04 Jul 2008 06:27:42 GMT, "Graham" wrote:

Does anyone know if these gauges display miles per gallon (or litres per
km)
or just miles travelled and gallons consumed?

Do they need any special interface to work with standard GPS's like a
Raytheon chart plotter?

Thanks, Graham

Check this - don't know if it applies to yours.
About halfway down is pic.

http://www.thehulltruth.com/forums/t...tart=1&posts=1

--Vic

On Fri, 4 Jul 2008 11:18:42 -0400, "Jim" wrote:


"Richard Casady" wrote in message
.. .
On Fri, 4 Jul 2008 06:29:26 -0400, "Jim" wrote:


"Graham" wrote in message
news:ypjbk.54744$Jx.31786@pd7urf1no...
Does anyone know if these gauges display miles per gallon (or litres per
km) or just miles travelled and gallons consumed?

Do they need any special interface to work with standard GPS's like a
Raytheon chart plotter?

Thanks, Graham

The GPS reports miles per hour over land. It would be useless to use those
calculations in determining real miles per gallon over the surface of the
water.

It reports MPH everywhere equally well. It doesn't know sea from land
unless you get it wet. It reports speed over the land and if the land
is flooded, at sea or on a river,






THIS IS THE WHOLE POINT. If you are heading against a 5 kt current at 10
kts, what speed will the GPS report?


there may be an effect from
currents.

Didn't think GPS cared about currents.
If you want to know how fast you're going toward your destination, GPS
can tell you.
If you want to know how fast the water is moving past your speedo
pitot, the boat speedo tells you that - assuming it's working
correctly.
This is what I've heard, anyway.
The graphic (DIP switches) in the link I provided shows the Yamaha
speed sensor can be set to speedo or GPS (NMEA0183.)
Fuel metering DIP can be set for GPH and l/h only.
Looks like no translation to MPG.
All info is good if you make use of it.
So if you assume the boat owner knows his burn per hour (I'd trust
engine rpm more than a fuel flow meter *usually*) and is making a long
run toward a destination, say 100 miles, the GPS speedo is valuable in
calculating whether his fuel will get him there. If it did the
translation and was accurate it would be better.
On some engines a fuel pump/regulator diaphragm can develop a leak and
lose fuel to the intake manifold without real obvious signs. A flow
meter might come in handy for detecting that.
Personally I've found just counting the gallons pumped into the tank
gets me a good enough handle on car mileage. A flow meter seems good
for boats to determine most economical rpm.
From what I've heard the car/boat flowmeters are better at finding the
"best" spot than they are at actually measuring the flow spot exactly.
For instance a guy is reporting he's getting 34 mpg at 65mph on his
car and 31mpg at 75 mph according to his flowmeter.
He's really getting 32 and 29mpg. But the meter does accurately tell
him he's using less fuel at 65mph.
If all or any of the that is wrong let me know.
Your question about a 5kt current and 10kt speed for example.
I think you have to add "apparent" or "true" to the 10kt part to
answer that, but I'm not sure.
Already got a headache.

--Vic

"Short Wave Sportfishing" wrote in message
...
On Fri, 04 Jul 2008 10:12:05 -0400, HK wrote:

Short Wave Sportfishing wrote:
On Fri, 04 Jul 2008 08:25:15 -0400, Gene Kearns
wrote:

On Fri, 4 Jul 2008 06:29:26 -0400, Jim penned the following well
considered thoughts to the readers of rec.boats:

"Graham" wrote in message
news:ypjbk.54744$Jx.31786@pd7urf1no...
Does anyone know if these gauges display miles per gallon (or litres
per
km) or just miles travelled and gallons consumed?

Do they need any special interface to work with standard GPS's like a
Raytheon chart plotter?

Thanks, Graham
The GPS reports miles per hour over land. It would be useless to use
those
calculations in determining real miles per gallon over the surface of
the
water.
Au contraire, mon ami!

The Yamaha fuel management gages must receive a fuel flow and GPS (or
speedometer... IMHO,useless) input. You must provide the GPS. I'm not
sure what format(s) of in/output are acceptable, but I suspect it is
configurable to standard formats IOW.... I don't think any special
interface is necessary (since you are likely using the Command Link
interface, already), if the GPS unit outputs a format recognizable to
the FMM..

http://www.yamaha-motor.com/outboard...nk/page05.aspx

No, I think Jim is right.

The link doesn't really give you any information on what data sets are
actually being shared and what format - I would assume NEMA 183.X
which is the defacto standard. The major issue would be connectors on
that harness they supply and how compatiable it is with other units.
However, being NEMA 183 systems, the connector to the hub has to be
something standard - maybe like a N connector or RCA jack.

To the point though, what purpose would having a fuel flow meter do a
calculation based on GPS? The calculation would be simpler and more
efficient to take the fuel flow data in GPH and base the rest of the
calculation on that - position has nothing to do with fuel usage. GPH
has a direct correlation to RPM and MPG - why complicate things?

For instance, if the metering system does the calculations and you
select MPG, then you know if you are using more or less fuel to reach
your destination - X miles equals Y fuel (or the inverse - Y fuel
equals X miles). Same with GPH - X miles equals Y operating time
equals Z available miles.

GPS has nothing to do with fuel usage.

Well, this has been a fun read so far.

There are *two* different Yamaha gauges available that display fuel usage.

One is a fuel management meter unit. The other is a speed and fuel meter
unit. Interestingly, the "speed sensor" on the engine is incredibly
accurate, at least it is on my boat. It gives just about the same
reading as the GPS at all times that I have noticed.

The fuel management meter shows flow, fuel available, total consumption,
and miles or nautical miles per gallon. Metric read-outs are also
available.

The speed and fuel meter unit does not display the amount of fuel
available. But it does have functions not available on the fuel
management meter.

That's similar to the unit I have with the ETEC.

I have the Command Link Multifunction Meter Installation Manual somewhere.

I'd be curious what the data format is and what version.

Still doens't answer the question though - why bother with hooking a
GPS into the system?

Speed over ground and speed in water will average out to about the same in a
day of running. Sometimes with the current and others against the current.
And how many people in lakes and ocean are running against large currents
for a long time?

On Fri, 04 Jul 2008 13:49:02 GMT, Short Wave Sportfishing
wrote:

GPS has nothing to do with fuel usage.

No, it's just a tool used for management of fuel use.

Casady

On Fri, 04 Jul 2008 11:39:02 -0400, Gene Kearns
wrote:

GPH is pretty meaningless when one wants to determine fuel consumed
per distance traveled. Miles per gallon is really what we want to
know, since that is a better measure of fuel economy. (Least fuel
consumed, per mile, is my goal, anyway.)

Please take no offense, but that doesn't make any sense.

You have to have a base calculation which would be gallons per hour
(actually I've been told that the true base is per minute) because
it's the only true way to measure fuel usage.

Thus, you use X fuel over Y time.

So what can be the variable in the equation - RPM. At low RPM,
G(used)PH goes down and when RPM rises, G(used)PH goes up.

Thus, at A revolutions you use X Fuel over Y time.

That cannot change - it's the base calculation.

Now from there, you can make whatever calculation you want - furlongs
per fortnight or miles per gallon - it doesn't matter because it's all
based on GPH. It can't be any other way.

Feed distance, time, and gallons consumed into the computer and out
comes MPG.

That's fine, but it's still the same number as GPH. You have still
used a certain amount of Gallons Per Hour.

You asked a question in another post:

Heading upstream in a 10 MPH current at 8 MPH would give what
sort of MPG???? Sooner or later the fuel tank would overflow...!

That's exactly the point of GPH - you have a known figure.

If your not making headway, you are still using fuel - GPH again.

On Fri, 04 Jul 2008 15:53:58 GMT, "Graham" wrote:

Thanks for the rapid information Vic and to all the others who have posted
interesting comments here

The gps input helps measure the actual speed made good over the ground which
is needed for calculation of best speed for fuel consumption in litres/km
relative to the ground which is what I'm interested in (ie starting and
ending points of my trips are attached to the earth!)

I give up. :)

On Fri, 4 Jul 2008 10:14:30 -0700, "Calif Bill"
wrote:

And how many people in lakes and ocean are running against large currents
for a long time?

Heh, ever been near the Gulf Stream?

On Fri, 04 Jul 2008 18:34:18 GMT, (Richard
Casady) wrote:

On Fri, 04 Jul 2008 13:49:02 GMT, Short Wave Sportfishing
wrote:

GPS has nothing to do with fuel usage.

No, it's just a tool used for management of fuel use.

I've given up trying to understand why. :)

"Short Wave Sportfishing" wrote in message
...
On Fri, 04 Jul 2008 11:39:02 -0400, Gene Kearns
wrote:

GPH is pretty meaningless when one wants to determine fuel consumed
per distance traveled. Miles per gallon is really what we want to
know, since that is a better measure of fuel economy. (Least fuel
consumed, per mile, is my goal, anyway.)

Please take no offense, but that doesn't make any sense.

You have to have a base calculation which would be gallons per hour
(actually I've been told that the true base is per minute) because
it's the only true way to measure fuel usage.

Thus, you use X fuel over Y time.

So what can be the variable in the equation - RPM. At low RPM,
G(used)PH goes down and when RPM rises, G(used)PH goes up.

Thus, at A revolutions you use X Fuel over Y time.

That cannot change - it's the base calculation.

Now from there, you can make whatever calculation you want - furlongs
per fortnight or miles per gallon - it doesn't matter because it's all
based on GPH. It can't be any other way.

Feed distance, time, and gallons consumed into the computer and out
comes MPG.

That's fine, but it's still the same number as GPH. You have still
used a certain amount of Gallons Per Hour.

You asked a question in another post:

Heading upstream in a 10 MPH current at 8 MPH would give what
sort of MPG???? Sooner or later the fuel tank would overflow...!

That's exactly the point of GPH - you have a known figure.

If your not making headway, you are still using fuel - GPH again.

There are simply too many variables to calculate MPH over water. You can use
a GPS log of total miles traveled to calculate MPG of a particular trip.
That won't necessarily compare to the same trip on a different day. You can
collect data and come up with averages if you want. That might be useful.
You can reliably chart GPH at given throttle positions and then convert
throttle position to approximate MPH(over water, not land). You and I are on
the same page but the other folks don't buy into what we are saying. No big
deal.