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Gallons per hour vs miles per gallon
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 |
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 |
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 |
On Wed, 11 May 2005 15:07:02 -0400, John H
wrote: 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. I don't have one on the Ranger, but I do on the Contender. Of course, I have no idea what the GPH figure is on the Contender BECAUSE THEY HAVEN'T FINISHED INSTALLING THE FREAKIN' THRU-HULL AND OR PAINTED THE BOTTOM!!!! AARRRGGGHHHH!!!! Later, Tom |
On 11 May 2005 12:56:41 -0700, "Camilo" wrote:
~~ snippage ~~ 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. I mean no offense here. Don't get upset - just follow me through this. To do a MPG calculation you basically need to know how many miles you have traveled. Which means that you either need to know that by experience or stop to use a chart or take a measurement with a GPS. Now, you already know how many gallons you are using per hour. So all you need to do is know how much gas is in your boat and how many hours you have been traveling. That seems a hell of a lot easier than doing arithmetical calculations on the fly. And just to add a complication, let's say that your GPS is kaput for some reason. You have no idea how many miles you have traveled, but you have a good idea of how many gallons you have left and how much time it takes to return. That's a GPH calculation, yes? Later, Tom |
On Wed, 11 May 2005 21:26:39 GMT, Gene Kearns
wrote: 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? Hmmm.. there seems to be some games with semantics, here, but my take is that an engine can be expected to consume X gallons of fuel per hour to develop Y horsepower. One may then calculate the "miles per gallon" figure, but I fear it is of more interest to the marketing department than the practical boater. 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.... I think the GPH side has won the day. Therefore, I RULE!!! :) Later, Tom |
On Thu, 12 May 2005 00:08:02 GMT, otnmbrd
wrote: 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. Good points. Later, Tom |
Actually it is neither in this particular case.
If I am so stupid as to head out on a lake/river that I don't know without a chart or gps and I did not fill up my gas tank before leaving but I kept up w/ my time at various rpms then GPH at each of these rpms would mean something. On the other hand, assuming I at least filled the gas tank, as long as I have over 1/2 tank left (not what the needle says but actually 1/2 tank) I should be able to get back as long as I don't run any harder than I did getting to where I am. I use MPG as an overall average but GPH as an overall average works out to be the same thing. MPG I know I can run for 2.5 miles per gallon of fuel on average (averaging 40 miles per hour). This of course changes if I run wide open for long periods of time or idle along. GPH I know I can run one hour on 16 gallons of fuel on average (averaging 40 miles per hour). This of course changes if I run wide open for long periods of time or idle along. Both work just as good. -- Tony my boats and cars at http://t.thomas.home.mchsi.com - "Shortwave Sportfishing" wrote in message ... On 11 May 2005 12:56:41 -0700, "Camilo" wrote: ~~ snippage ~~ 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. I mean no offense here. Don't get upset - just follow me through this. To do a MPG calculation you basically need to know how many miles you have traveled. Which means that you either need to know that by experience or stop to use a chart or take a measurement with a GPS. Now, you already know how many gallons you are using per hour. So all you need to do is know how much gas is in your boat and how many hours you have been traveling. That seems a hell of a lot easier than doing arithmetical calculations on the fly. And just to add a complication, let's say that your GPS is kaput for some reason. You have no idea how many miles you have traveled, but you have a good idea of how many gallons you have left and how much time it takes to return. That's a GPH calculation, yes? Later, Tom |
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I know when the gas guage stops bouncing, I need to be near a gas station.
"Shortwave Sportfishing" wrote in message ... On 11 May 2005 12:56:41 -0700, "Camilo" wrote: ~~ snippage ~~ 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. I mean no offense here. Don't get upset - just follow me through this. To do a MPG calculation you basically need to know how many miles you have traveled. Which means that you either need to know that by experience or stop to use a chart or take a measurement with a GPS. Now, you already know how many gallons you are using per hour. So all you need to do is know how much gas is in your boat and how many hours you have been traveling. That seems a hell of a lot easier than doing arithmetical calculations on the fly. And just to add a complication, let's say that your GPS is kaput for some reason. You have no idea how many miles you have traveled, but you have a good idea of how many gallons you have left and how much time it takes to return. That's a GPH calculation, yes? Later, Tom |
Around 5/11/2005 5:20 PM, Shortwave Sportfishing wrote:
On Wed, 11 May 2005 15:01:56 -0400, Mike G wrote: 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 snip 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. snip I like GPH just because I know that after about two hours of cruising, it's time to switch to the other tank. MPG (as measured with a GPS) isn't nearly as consistent. :) -- ~/Garth - 1966 Glastron V-142 Skiflite: "Blue-Boat" "There is nothing - absolutely nothing - half so much worth doing as simply messing about in boats." -Kenneth Grahame, The Wind in the Willows |
On Thu, 12 May 2005 01:15:25 GMT, "tony thomas"
wrote: Both work just as good. True, but one relies more on technology rather than seat of the pants reckin' :) Later, Tom |
On Thu, 12 May 2005 02:44:18 GMT, "Bill McKee"
wrote: I know when the gas guage stops bouncing, I need to be near a gas station. ROTFL!!! Damn straight. :) Later, Tom |
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That you should be out fishing!
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On 12 May 2005 13:09:09 -0700, "Camilo" wrote:
That you should be out fishing! Well that goes without saying. :) Later, Tom |
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? Just use a GPS and get a fuel gauge. Once your tank reads half, turn around and go back. Simple. Me and the wife http://pg.photos.yahoo.com/ph/harkra...bum?.dir=/1323 |
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