My 90 yamaha came with a twin gauge system with fuel flow, mpg or nmpg, trip total, total miles etc. I recall thinking "that can't be" first time to wot. Gps said 28 knots. Fuel flow said 9gph! But still about 3.2 plus mpg Here we pay about $6 a gallon. I find using my meters as a guide, real world I get a bit better than it says. The thing I like on my 22 is the visible tank level. I try to carry " mission fuel" with reserve. Just out for the weekend in the gulf islands I don't need 50 gallons. I am amazed also by how long fuel lasts if I keep to lower speeds. If we potter about, we can cruise a good long while I tend to spend more in pubs on lunch overall! Keeping these boats light in the stern helps. :smiled Mr Toland draws some nice boats!
Fuel flow and economy - Marinaut 215
- Thread starter Les Lampman
- Start date
Someplace back up there in this thread somebody mentioned :shock: :roll: 
surprise at mentioning MPG and boats in the same sentence. I think likewise. For many of us, boating on salt water, MPG measurement is lunacy. Speed measured by GPS is inaccurate, even if "your" GPS can put you into a 3 foot circle on planet earth.
Today I left Mystery Bay at 1130 and according to my GPS I covered 22.8 miles. Yup. That is a fact. Because The points on the globe did not change in their relationships to each other. How far did I travel on the water. It is probably possible to figure, but I don't have the math skills or the patience, or precise enough records to figure it out. Lets see, the tide was running out of Kilisut harbor, so I was riding down hill on the tide. Then it changed and then it was running against me on the way around the point (Wilson) and when I got to Sequim Bay, it was pushing in, so I got more free ride. Tide running with me. Free miles, or fewer water miles actually traveled. Running against the tide, GPS says I'm running at 13 knots. Hmmm. Same throttle setting as I had before when I was doing 16.5 knots.
Really, I think it is insane to be trying to figure MPG here. It might work on a lake, but anywhere else, ocean or river, it is a flawed measurement. (Hey Rich, I am not Harping at you. I think it is cool that you have done all the measurements. the more you do of that the more comfortable you are with range in relation to fuel on board.)
Because of frequent changing conditions, even Gallons per hour (GPH) numbers are hard to justify. (At least for me.) I like my fuel visible tanks, and use the 1/3rd rule (1/3 out, 1/3 back and 1/3 for reserve.) AND I like the slow cruise fuel consumption as well as the availability of the on plane speed if i feel the need.
One thing I would like to do, is figure out how to effectively calibrate the paddle wheel speeds to accurately reflect the speed over the water. That should equal either the minus or plus of the current speed and the GPS speed to show me the real difference.
Still things to learn.
Harvey
SleepyC :moon
surprise at mentioning MPG and boats in the same sentence. I think likewise. For many of us, boating on salt water, MPG measurement is lunacy. Speed measured by GPS is inaccurate, even if "your" GPS can put you into a 3 foot circle on planet earth.Today I left Mystery Bay at 1130 and according to my GPS I covered 22.8 miles. Yup. That is a fact. Because The points on the globe did not change in their relationships to each other. How far did I travel on the water. It is probably possible to figure, but I don't have the math skills or the patience, or precise enough records to figure it out. Lets see, the tide was running out of Kilisut harbor, so I was riding down hill on the tide. Then it changed and then it was running against me on the way around the point (Wilson) and when I got to Sequim Bay, it was pushing in, so I got more free ride. Tide running with me. Free miles, or fewer water miles actually traveled. Running against the tide, GPS says I'm running at 13 knots. Hmmm. Same throttle setting as I had before when I was doing 16.5 knots.
Really, I think it is insane to be trying to figure MPG here. It might work on a lake, but anywhere else, ocean or river, it is a flawed measurement. (Hey Rich, I am not Harping at you. I think it is cool that you have done all the measurements. the more you do of that the more comfortable you are with range in relation to fuel on board.)
Because of frequent changing conditions, even Gallons per hour (GPH) numbers are hard to justify. (At least for me.) I like my fuel visible tanks, and use the 1/3rd rule (1/3 out, 1/3 back and 1/3 for reserve.) AND I like the slow cruise fuel consumption as well as the availability of the on plane speed if i feel the need.
One thing I would like to do, is figure out how to effectively calibrate the paddle wheel speeds to accurately reflect the speed over the water. That should equal either the minus or plus of the current speed and the GPS speed to show me the real difference.
Still things to learn.
Harvey
SleepyC :moon
starcrafttom
Active member
Harvey, the GPS is showing how fast the boat is moving forward. It does not care what the tide is doing. Your true speed is gps speed. The paddle wheel can be higher then true speed if you are going against the current and lower is with the current. I set my screen to show both so I know when I am getting a push or not.
as for mpg. yes it will be lower against a current but its higher in my car up a hill to??? whats the point. You are looking for a day long average.
I only worry about my fuel burn to plan a trip or a run on a trip. I have learned that my boat gets 2.2 to 2.5 mpg as long as I'm on plane. I get these numbers depending on water condition any where above 13 mph. From there to 30mph I get the same milage. After that it starts to really suck down the gas.
as for mpg. yes it will be lower against a current but its higher in my car up a hill to??? whats the point. You are looking for a day long average.
I only worry about my fuel burn to plan a trip or a run on a trip. I have learned that my boat gets 2.2 to 2.5 mpg as long as I'm on plane. I get these numbers depending on water condition any where above 13 mph. From there to 30mph I get the same milage. After that it starts to really suck down the gas.
Tom,
Right GPS is showing speed over ground. NOT true boat speed on the water. As you say the tidal influence is plus or minus. Agreed.
I agree with you about the design factor. Wider flatter aft section equals more lift and planing surface, more bouyancy.
Oh, and sailers and slow cruisers spend their cruising "day" running downstream or with the tide, not usually by accident, increasing their daytime travel distance, (or milage
Harvey
SleepyC :moon
Right GPS is showing speed over ground. NOT true boat speed on the water. As you say the tidal influence is plus or minus. Agreed.
I agree with you about the design factor. Wider flatter aft section equals more lift and planing surface, more bouyancy.
Oh, and sailers and slow cruisers spend their cruising "day" running downstream or with the tide, not usually by accident, increasing their daytime travel distance, (or milage
Harvey
SleepyC :moon
Les Lampman
New member
hardee":3o5xek23 said:Someplace back up there in this thread somebody mentioned :shock: :roll:
Today I left Mystery Bay at 1130 and according to my GPS I covered 22.8 miles. Yup. That is a fact. Because The points on the globe did not change in their relationships to each other. How far did I travel on the water. It is probably possible to figure, but I don't have the math skills or the patience, or precise enough records to figure it out. Lets see, the tide was running out of Kilisut harbor, so I was riding down hill on the tide. Then it changed and then it was running against me on the way around the point (Wilson) and when I got to Sequim Bay, it was pushing in, so I got more free ride. Tide running with me. Free miles, or fewer water miles actually traveled. Running against the tide, GPS says I'm running at 13 knots. Hmmm. Same throttle setting as I had before when I was doing 16.5 knots.
Really, I think it is insane to be trying to figure MPG here. It might work on a lake, but anywhere else, ocean or river, it is a flawed measurement. (Hey Rich, I am not Harping at you. I think it is cool that you have done all the measurements. the more you do of that the more comfortable you are with range in relation to fuel on board.)
Because of frequent changing conditions, even Gallons per hour (GPH) numbers are hard to justify. (At least for me.) I like my fuel visible tanks, and use the 1/3rd rule (1/3 out, 1/3 back and 1/3 for reserve.) AND I like the slow cruise fuel consumption as well as the availability of the on plane speed if i feel the need.
One thing I would like to do, is figure out how to effectively calibrate the paddle wheel speeds to accurately reflect the speed over the water. That should equal either the minus or plus of the current speed and the GPS speed to show me the real difference.
Still things to learn.
Harvey
SleepyC :moon
Harvey,
When you're operating in a fluid medium like water or air you can't get the same precision you can when operating, say, a vehicle. Still, you need some way to predict either how many miles you can typically run between fill ups or how many hours you can run between fill ups. Without one or the other it's a guessing game.
Your 1/3 out, 1/3 back, and 1/3 reserve is fine and a nice safe approach. But what happens when you want to go somewhere? I doubt seriously that if I put you aboard a boat with a full tank and you didn't know how many gallons the tank (or tanks) held you'd be a bit concerned if I said the next fuel was 100 miles away. Your 1/3 out and 1/3 back isn't going to help you very much unless you know that the 2/3 you're allowing yourself to burn is sufficient to make the distance. The way you estimate that is to know how many miles (in general) 2/3 of your fuel will take you or you can figure how much time (in general) it will take to make the run and then figure out how long you can run on the allotted fuel (based on GPH). Either way you're figuring miles-per-gallon or gallons-per-hour even if you're not calling it that. The only way that 1/3 out, 1/3 back, and 1/3 reserve works with no knowledge of fuel burn is if you have no set agenda (that is, no destination) and turn around as soon as you're down 1/3, or you've done the run before and know it's do-able.
It is true that MPG may be more variable in boats than in vehicles but it's still a number that an operator should have in mind (and gallons-per-hour is just another way of saying miles-per-gallon so it counts too) so that one has an idea of whether or not a particular run is achievable. Prudence would suggest that one not use optimum fuel economy for planning purposes but nevertheless some number must be factored in to decide whether or not a destination is reachable with the fuel onboard. So figuring MPG (or its close sibling GPH) is not lunacy at all, having no idea how far (or how long) your onboard fuel will take would be the lunatic part.
Rough water always takes more fuel than calm water, if you know your boat well you generally have a feel for how much more. Current, in saltwater or rivers, is also a factor and must be accounted for whether you're figuring in MPG or GPH if you're route planning.
I'd bet dollars to donuts you wouldn't like to be aboard an airplane if the pilot told you s/he had no idea how far the plane could go or how long it could stay aloft, and that s/he would just fly until 1/3 of the fuel was used then turn back. An aircraft has the same fluid medium issue we have with boats and they don't get a specific MPG either. Usually small aircraft use GPH and in route planning they figure winds aloft and compensate accordingly so they know whether or not the planned fuel stops are prudent (the big boys use pounds of fuel per hour but it's the same process). If you know your GPH rate and the distance you're flying it's not hard to figure MPG.
No information with regard to boat operation, safety, and range should be considered idiotic or lunatic. It all adds up to knowing more about what your boat can or can not achieve. You may not think MPG is very accurate (and it really isn't) but if you totally ignore it (and don't use the related GPH) you really have no clue whether or not you can make a particular destination.
Your boat speed through the water has no effect on how many miles you travel from one point to another. As you say those points on earth do not change (or at least not a rate that affects us during a boat trip). If the GPS says you covered "X" miles than you traveled "X" miles regardless of the speed, or what the current did, or what the wind did. If you fill up your boat, travel "X" distance (GPS miles), fill your boat up again, and then divide the distance by fuel used you will get a precise MPG (and GPH if you noted the times) for that trip. That doesn't mean for any other trip it's repeatable but for that trip is was accurate.
You GPS is speed over the ground and not through the water. If you travel "X" miles at a specific GPS speed it will always take the same amount of time and cover the same distance; that's not variable. If you set your throttle at a particular setting your speed through the water will be (relatively) constant but your GPS speed (speed over the ground) will vary. Let's say in calm water you set your throttle for 12 knots of water speed and in this case (since we have no current or wind) the water speed and the ground speed are the same 12 knots. If we introduce a 3 knot current on the bow then your water speed will remain at 12 knots but your ground speed will drop to 9 knots. If we introduce a 3 knot current on the stern then your water speed will remain at 12 knots but your ground speed will increase to 15 knots.
Figuring MPG is not insane here at all; it's simply the miles covered divided by the fuel used, both of which are attainable figures. It is true that MPG is different in each direction (in the example above) but that doesn't make it useless or impossible to figure. My truck mileage varies a lot with what I'm towing and whether or not I'm on the prairies or in the mountains but I still calculate it so I have a better idea of where I need to stop for fuel next. It can vary from 7.5 MPG to 12.5 MPG so the swing is not inconsequential (and probably worse than on most boats).
What kind of system is the paddle wheel on your boat connected to (make, model, etc)? Many have a way to calibrate the paddle wheel.
Les said:
Maybe insane is a bit strong.
Agreed, Not repeatable unless you can repeat the same tide, wind, wave, traffic and debris pattens. So on a straight out run, I figure I have about 100 miles worth, so I am looking at fill up at around 80 - 90 miles, but in reality, when I fill at even 100 miles, I still have ~3-5 gal left in each tank, sometimes more. Admittedly I have only done a couple of long distance straight runs like that, but when I calculate fuel use I used 3 mpg and then looked at the tide and currents to take advantage of keeping the current with me. Most trips like that are to the San Juans and back. 40 to Friday Harbor and back and that allows for some wiggle wobble.
The paddle wheel is on a RayMarine transducer connected to a C-120. My GPS speeds are coming from a Garmin, which I use for Speed and Distance covered as well as moving average and trip timing..
Thanks Les, for your explanations.
Harvey
SleepyC :moon
Maybe insane is a bit strong.
Agreed, Not repeatable unless you can repeat the same tide, wind, wave, traffic and debris pattens. So on a straight out run, I figure I have about 100 miles worth, so I am looking at fill up at around 80 - 90 miles, but in reality, when I fill at even 100 miles, I still have ~3-5 gal left in each tank, sometimes more. Admittedly I have only done a couple of long distance straight runs like that, but when I calculate fuel use I used 3 mpg and then looked at the tide and currents to take advantage of keeping the current with me. Most trips like that are to the San Juans and back. 40 to Friday Harbor and back and that allows for some wiggle wobble.
The paddle wheel is on a RayMarine transducer connected to a C-120. My GPS speeds are coming from a Garmin, which I use for Speed and Distance covered as well as moving average and trip timing..
Thanks Les, for your explanations.
Harvey
SleepyC :moon
Seriously -- I love this forum, its people, and our Marinaut. I really don't care to compare Marinaut fuel economy to C-Dory's, because I think that C-Dory's are wonderful, fuel efficient boats. Please remember that I used to have a CD 16 Cruiser and loved it! By the way, the CD 16 could do well over 5 MPG. When I removed the 4 Stroke 4 Horsepower kicker from the stern, she was hitting 6+ mpg at slack. So when Les was talking about stern weight, he was dead on. C-Dory's tend to be stern heavy, and my boat was more so because the Suzuki 40 HP weighed more than its competitors. Combine that weight with a 50 pound kicker and extra fuel, and she was seriously stern heavy.
I think my approach of counting on 4.5 mog for planning purposes is very sound, and its accuracy is is born out by the data. So if some of you feel my approach is not possible in the ocean, then why am I getting such consistent results when it flies in the face of everything you know? I'm certainly not as experienced as many of you, so there must be something else at play. Here is what I think.
1) The waters in the PNW are big -- real big at times, with swift currents. Long Island Sound can be choppy, but the currents are relatively docile. So really, I don't travel on the ocean, I travel on the Sound.
2) Even though the Marinaut can take heavy seas, I wait for NOAA to predict seas of 1 foot or less, and then venture out. In that way, if we hit 2 or 3 feet, we'll be fine. So we may be traveling is more benign condition then you.
3) The channel entering into Niantic Bay can get really rough when the tide is moving. So I plan our trips accordingly. As you saw from an earlier post, if we plan to go out with the tide and come back with the tide, we can do much higher then our YTD average of 4.6 MPG. The point is that it is easy for me to do this, whereas in your cruising grounds, it may be an entirely different story.
4) We spend a lot of time cruising in the even more docile interior of Long Island. We love it. We also spend a lot of time on the Connecticut River, and when we sail to Narraganset bay, we make sure the water is docile!
5) We travel fast quite often. The most efficient mode for our engine is 3,500 RPM at around 20 knots. This gives us the best mileage at planing speed. Obviously, in the displacement mode of speeds less than 6 mph is the most efficient.
6) I may use the fuel flow meter more than most of you, so this gives me a good idea of the most efficient operating speed. Although I'm beginning to get a good feel for the boat, when not looking at the fuel flow meter, I care more about engine RPMs as opposed to the speedometer.
7) As stated in previous posts, our normal round trip is 45 miles. We did take a 130 mile round trip this year, but that is not the norm. So there are not a lot of surprises encountered when taking shorter trips. Many of you take much longer trips where you encounter more varied conditions.
Eight) I avoid semi-displacement speeds. If I'm not planing, I'll slow it down to displacement. There are, of course exceptions. So seamanship is part of it like using the right speed in following seas so as to ride the crests and to avoid falling off the backs of waves. The Marinaut surfs very well, and she subtly informs us if we need to let off the throttle. Not always traveling in a straight line when heading into heavy current and wave action is important. If I make smooth and subtle throttle adjustments, and am not too impatient to get onto plane, the boat is running more efficiently. (Although I must confess that with Honda BLAST system, its fun to make the boat jump out of the hole! I'll bet the Marinaut w/BF115 could do a good job at pulling a water skier.)
So I've done 1,000 miles this year, and I'm extremely confident that 4.5 mpg is a rational planning number -- for me. Take the same Marinaut, and transport it to Alaska, for example, and if there are heavier seas there where a person is forced to travel for extended distances in radically different conditions, then perhaps the numbers would be different, albeit I'm confident that it would nevertheless be impressive. So you see: the group is not wrong, and neither am I. It all has to do with where, when and how one cruises.
Rich :smile
I think my approach of counting on 4.5 mog for planning purposes is very sound, and its accuracy is is born out by the data. So if some of you feel my approach is not possible in the ocean, then why am I getting such consistent results when it flies in the face of everything you know? I'm certainly not as experienced as many of you, so there must be something else at play. Here is what I think.
1) The waters in the PNW are big -- real big at times, with swift currents. Long Island Sound can be choppy, but the currents are relatively docile. So really, I don't travel on the ocean, I travel on the Sound.
2) Even though the Marinaut can take heavy seas, I wait for NOAA to predict seas of 1 foot or less, and then venture out. In that way, if we hit 2 or 3 feet, we'll be fine. So we may be traveling is more benign condition then you.
3) The channel entering into Niantic Bay can get really rough when the tide is moving. So I plan our trips accordingly. As you saw from an earlier post, if we plan to go out with the tide and come back with the tide, we can do much higher then our YTD average of 4.6 MPG. The point is that it is easy for me to do this, whereas in your cruising grounds, it may be an entirely different story.
4) We spend a lot of time cruising in the even more docile interior of Long Island. We love it. We also spend a lot of time on the Connecticut River, and when we sail to Narraganset bay, we make sure the water is docile!
5) We travel fast quite often. The most efficient mode for our engine is 3,500 RPM at around 20 knots. This gives us the best mileage at planing speed. Obviously, in the displacement mode of speeds less than 6 mph is the most efficient.
6) I may use the fuel flow meter more than most of you, so this gives me a good idea of the most efficient operating speed. Although I'm beginning to get a good feel for the boat, when not looking at the fuel flow meter, I care more about engine RPMs as opposed to the speedometer.
7) As stated in previous posts, our normal round trip is 45 miles. We did take a 130 mile round trip this year, but that is not the norm. So there are not a lot of surprises encountered when taking shorter trips. Many of you take much longer trips where you encounter more varied conditions.
Eight) I avoid semi-displacement speeds. If I'm not planing, I'll slow it down to displacement. There are, of course exceptions. So seamanship is part of it like using the right speed in following seas so as to ride the crests and to avoid falling off the backs of waves. The Marinaut surfs very well, and she subtly informs us if we need to let off the throttle. Not always traveling in a straight line when heading into heavy current and wave action is important. If I make smooth and subtle throttle adjustments, and am not too impatient to get onto plane, the boat is running more efficiently. (Although I must confess that with Honda BLAST system, its fun to make the boat jump out of the hole! I'll bet the Marinaut w/BF115 could do a good job at pulling a water skier.)
So I've done 1,000 miles this year, and I'm extremely confident that 4.5 mpg is a rational planning number -- for me. Take the same Marinaut, and transport it to Alaska, for example, and if there are heavier seas there where a person is forced to travel for extended distances in radically different conditions, then perhaps the numbers would be different, albeit I'm confident that it would nevertheless be impressive. So you see: the group is not wrong, and neither am I. It all has to do with where, when and how one cruises.
Rich :smile
Hi Rich,
Sorry I did not mean to get into a "comparing C-dory to Marinaut" streak. The differences in the boats are pretty blatant and yet there are similarities too. From the sounds of your reports, you are pretty good at picking cruises days. And maybe the waters are more docile there. The PNW waters are pretty often, pretty mixed up. That is part of the challenge I enjoy working to negotiate. Having been a lifelong sailer, using the currents to my advantage is almost second nature, so often times, my trips from A to B include several angles, and often different speeds. I have only recently started including more detailed fuel and time data into my log. Not sure how much good it is going to do, but it sure can't hurt. At some point I want to go north to Alaska and prior to that, I will add more fuel storage capability, (saddle tanks) to move the weight forward, and increase the size of the trim tabs to help add some stern lift also.
I understand and agree that we each have different boats (even the CD's are different in that they get different mods, loads, and rigging so the are not exactly the same all around either.) As Rogerbum said in a different thread, the enjoyment per $ is what it is about. Some enjoy getting farther per $ and some enjoy getting there sooner. Some like to carry more gear, and some are minimalists. We each want to enjoy our boat, in our own way. And sharing how we do that on this site is part of the enjoyment. (Of course it also helps the rest of us not have to re-invent the wheel every weekend too.) So thanks for your effort, and for your sharing.
And to Les and Dave for their efforts in producing a really fine new line. And glad to see it here. And always to Les for all his participation, offerings and insights here.
Harvey
SleepyC :moon
Sorry I did not mean to get into a "comparing C-dory to Marinaut" streak. The differences in the boats are pretty blatant and yet there are similarities too. From the sounds of your reports, you are pretty good at picking cruises days. And maybe the waters are more docile there. The PNW waters are pretty often, pretty mixed up. That is part of the challenge I enjoy working to negotiate. Having been a lifelong sailer, using the currents to my advantage is almost second nature, so often times, my trips from A to B include several angles, and often different speeds. I have only recently started including more detailed fuel and time data into my log. Not sure how much good it is going to do, but it sure can't hurt. At some point I want to go north to Alaska and prior to that, I will add more fuel storage capability, (saddle tanks) to move the weight forward, and increase the size of the trim tabs to help add some stern lift also.
I understand and agree that we each have different boats (even the CD's are different in that they get different mods, loads, and rigging so the are not exactly the same all around either.) As Rogerbum said in a different thread, the enjoyment per $ is what it is about. Some enjoy getting farther per $ and some enjoy getting there sooner. Some like to carry more gear, and some are minimalists. We each want to enjoy our boat, in our own way. And sharing how we do that on this site is part of the enjoyment. (Of course it also helps the rest of us not have to re-invent the wheel every weekend too.) So thanks for your effort, and for your sharing.
And to Les and Dave for their efforts in producing a really fine new line. And glad to see it here. And always to Les for all his participation, offerings and insights here.
Harvey
SleepyC :moon
As always Les is (of course) right (well almost always anyway :wink: ). To put things a bit differently, MPG (miles over ground) is not only not insane, in the end it's all that really matters. I don't drive to a point relative to the water, I drive to a point relative to the ground. E.g. if I'm going to Friday Harbor, all I really care about is distance over the ground and whether I make it to Friday Harbor with the fuel on board. In practice, I don't worry about current and water roughness (other than will it be comfortable enough to go/have fun). I take my average MPG (average since it averages over all these factors) reduce it a bit for safety (because today might be worse than average) and multiply by the gallons I have on board. If I can make it with a decent reserve in the amount of time I want to spend on this trip, then I go. If not, I add fuel. It's simple.
Les Lampman":qxh0zgj5 said:hardee":qxh0zgj5 said:Someplace back up there in this thread somebody mentioned :shock: :roll:
Today I left Mystery Bay at 1130 and according to my GPS I covered 22.8 miles. Yup. That is a fact. Because The points on the globe did not change in their relationships to each other. How far did I travel on the water. It is probably possible to figure, but I don't have the math skills or the patience, or precise enough records to figure it out. Lets see, the tide was running out of Kilisut harbor, so I was riding down hill on the tide. Then it changed and then it was running against me on the way around the point (Wilson) and when I got to Sequim Bay, it was pushing in, so I got more free ride. Tide running with me. Free miles, or fewer water miles actually traveled. Running against the tide, GPS says I'm running at 13 knots. Hmmm. Same throttle setting as I had before when I was doing 16.5 knots.
Really, I think it is insane to be trying to figure MPG here. It might work on a lake, but anywhere else, ocean or river, it is a flawed measurement. (Hey Rich, I am not Harping at you. I think it is cool that you have done all the measurements. the more you do of that the more comfortable you are with range in relation to fuel on board.)
Because of frequent changing conditions, even Gallons per hour (GPH) numbers are hard to justify. (At least for me.) I like my fuel visible tanks, and use the 1/3rd rule (1/3 out, 1/3 back and 1/3 for reserve.) AND I like the slow cruise fuel consumption as well as the availability of the on plane speed if i feel the need.
One thing I would like to do, is figure out how to effectively calibrate the paddle wheel speeds to accurately reflect the speed over the water. That should equal either the minus or plus of the current speed and the GPS speed to show me the real difference.
Still things to learn.
Harvey
SleepyC :moon
Harvey,
When you're operating in a fluid medium like water or air you can't get the same precision you can when operating, say, a vehicle. Still, you need some way to predict either how many miles you can typically run between fill ups or how many hours you can run between fill ups. Without one or the other it's a guessing game.
Your 1/3 out, 1/3 back, and 1/3 reserve is fine and a nice safe approach. But what happens when you want to go somewhere? I doubt seriously that if I put you aboard a boat with a full tank and you didn't know how many gallons the tank (or tanks) held you'd be a bit concerned if I said the next fuel was 100 miles away. Your 1/3 out and 1/3 back isn't going to help you very much unless you know that the 2/3 you're allowing yourself to burn is sufficient to make the distance. The way you estimate that is to know how many miles (in general) 2/3 of your fuel will take you or you can figure how much time (in general) it will take to make the run and then figure out how long you can run on the allotted fuel (based on GPH). Either way you're figuring miles-per-gallon or gallons-per-hour even if you're not calling it that. The only way that 1/3 out, 1/3 back, and 1/3 reserve works with no knowledge of fuel burn is if you have no set agenda (that is, no destination) and turn around as soon as you're down 1/3, or you've done the run before and know it's do-able.
It is true that MPG may be more variable in boats than in vehicles but it's still a number that an operator should have in mind (and gallons-per-hour is just another way of saying miles-per-gallon so it counts too) so that one has an idea of whether or not a particular run is achievable. Prudence would suggest that one not use optimum fuel economy for planning purposes but nevertheless some number must be factored in to decide whether or not a destination is reachable with the fuel onboard. So figuring MPG (or its close sibling GPH) is not lunacy at all, having no idea how far (or how long) your onboard fuel will take would be the lunatic part.
Rough water always takes more fuel than calm water, if you know your boat well you generally have a feel for how much more. Current, in saltwater or rivers, is also a factor and must be accounted for whether you're figuring in MPG or GPH if you're route planning.
I'd bet dollars to donuts you wouldn't like to be aboard an airplane if the pilot told you s/he had no idea how far the plane could go or how long it could stay aloft, and that s/he would just fly until 1/3 of the fuel was used then turn back. An aircraft has the same fluid medium issue we have with boats and they don't get a specific MPG either. Usually small aircraft use GPH and in route planning they figure winds aloft and compensate accordingly so they know whether or not the planned fuel stops are prudent (the big boys use pounds of fuel per hour but it's the same process). If you know your GPH rate and the distance you're flying it's not hard to figure MPG.
No information with regard to boat operation, safety, and range should be considered idiotic or lunatic. It all adds up to knowing more about what your boat can or can not achieve. You may not think MPG is very accurate (and it really isn't) but if you totally ignore it (and don't use the related GPH) you really have no clue whether or not you can make a particular destination.
Your boat speed through the water has no effect on how many miles you travel from one point to another. As you say those points on earth do not change (or at least not a rate that affects us during a boat trip). If the GPS says you covered "X" miles than you traveled "X" miles regardless of the speed, or what the current did, or what the wind did. If you fill up your boat, travel "X" distance (GPS miles), fill your boat up again, and then divide the distance by fuel used you will get a precise MPG (and GPH if you noted the times) for that trip. That doesn't mean for any other trip it's repeatable but for that trip is was accurate.
You GPS is speed over the ground and not through the water. If you travel "X" miles at a specific GPS speed it will always take the same amount of time and cover the same distance; that's not variable. If you set your throttle at a particular setting your speed through the water will be (relatively) constant but your GPS speed (speed over the ground) will vary. Let's say in calm water you set your throttle for 12 knots of water speed and in this case (since we have no current or wind) the water speed and the ground speed are the same 12 knots. If we introduce a 3 knot current on the bow then your water speed will remain at 12 knots but your ground speed will drop to 9 knots. If we introduce a 3 knot current on the stern then your water speed will remain at 12 knots but your ground speed will increase to 15 knots.
Figuring MPG is not insane here at all; it's simply the miles covered divided by the fuel used, both of which are attainable figures. It is true that MPG is different in each direction (in the example above) but that doesn't make it useless or impossible to figure. My truck mileage varies a lot with what I'm towing and whether or not I'm on the prairies or in the mountains but I still calculate it so I have a better idea of where I need to stop for fuel next. It can vary from 7.5 MPG to 12.5 MPG so the swing is not inconsequential (and probably worse than on most boats).
What kind of system is the paddle wheel on your boat connected to (make, model, etc)? Many have a way to calibrate the paddle wheel.
Les,
Very nice and detailed explanation.
rich
Some owners try to establish a boats average per hour fuel burn. They start out with full tanks and keep track of running time. Re fuel and divide fuel used by the hours run and you have a basic idea of what is going on with you fuel usage. Travel five hours burn 33 gallons you are burning around 6 .6 gallons an hour. I figure I get about 3mpg gallon travel 100 miles I have roughly burned around 33 gallons. Most folks that know their boats can achieve decent mileage by setting trim and loading the boat properly without fuel flow devices. Watching rpms and speed can tell you a lot. Staring at a fuel management screen for too long is distracted driving. Sooner or later the toys break and simple ways can come in handy. Warning this post was not designed to upset anyone. 
D.D.
D.D.
Les Lampman
New member
hardee":3s2jfzlj said:
Hi Harvey,
I don't have a C-series Raymarine at hand at the moment so I'm working from memory, if there are a few variances from what I write here hopefully your choices are apparent when you're looking at the display menus.
The Raymarine has a speed offset (in percentage) for the reported paddle wheel speed (just called "Speed" on the display, speed over ground is always SOG).
The easiest (but certainly not the only) way to access the setting is to choose a full screen sounder page on the C-120. Then press the 'menu' button on the right. From the pop up menu choose fishfinder setup menu (it should be the top choice). On the fishfinder setup menu you'll have lots of items but about midway down you should see your transducer listed (like P66, etc) and below that a menu choice for Speed Offset. If you highlight and choose that you'll get a small popup menu with speed offset in percentage. I use the rotating knob on the right side of the display to vary the percentage. As I recall I usually dial in about +125% variance on the CD22.
From what I can tell the C-120 will apply a straight percentage to all speeds. What that means is that you can't get it highly accurate throughout the whole range of speeds but you can get it dialed in very closely for the speed that's most important to you (like trolling speed or cruise speed).
When you first set it up it's easiest if you can find a chunk of water where you have no (or little) current and/or (higher) wind. Then you can keep tweaking the percentage to get the paddle wheel to match the Speed Over Ground from the GPS. If you can't do that don't worry about it. Just set it then pop in and refine it anytime you think you've got some very low current water around you. Once you get it set the difference between "Speed" (as labeled on the display) and SOG is the current and/or wind component (as you likely know already).
And thanks for the kind words!
Will-C":abickmac said:Some owners try to establish a boats average per hour fuel burn. They start out with full tanks and keep track of running time. Re fuel and divide fuel used by the hours run and you have a basic idea of what is going on with you fuel usage. Travel five hours burn 33 gallons you are burning around 6 .6 gallons an hour. I figure I get about 3mpg gallon travel 100 miles I have roughly burned around 33 gallons. Most folks that know their boats can achieve decent mileage by setting trim and loading the boat properly without fuel flow devices. Watching rpms and speed can tell you a lot. Staring at a fuel management screen for too long is distracted driving. Sooner or later the toys break and simple ways can come in handy. Warning this post was not designed to upset anyone.
D.D.
I'm not upset Dave, but surely -- you can't even begin to be serious to suggest that all I do is to stare at my fuel flow gauge so as to become distracted? If a boater travels in that neverland between displacement and plane, fuel consumption will deteriorate. If a boater goes WOT, fuel consumption goes through the roof. Heck -- visibility could be near zero, and a person could travel around in circles for hours like Mr. Magoo. A lot of good monitoring hours traveled would do for you in that circumstance. Call SeaTow! That's why most people, I think, see the value of tracking ground miles covered, as Les explained. Using the fuel flow and RPM meters serves to train the boater to get a feel for optimum settings. Think of it as biofeedback. As time goes on, you start to get a feel for things. But as I stated previously, you may subjectively think you are going efficiently, but unless you use technology to objectively validate your "feelings" how can you know for sure?
Approaches born from statements such as "basic idea", "figure I get" and "get about" may prove ultimately unsatisfying, as this subjective approach lacks the precision over more rigorous methods. I challenge you to try the mpg method next year, comparing it to your current methodology, and keep an open mind.
Rich
starcrafttom
Active member
Rich makes a great point. I bought the 27two years ago and kept track of gallons vs miles vs mph in my head when every I fueled up. I kept the speed down for the most part thinking that the best gph/mpg would be around 16 to 18 mph like my 22 or like most of what I was told by 25 owners. Well after the first year I installed a fuel meter. Justs gives total gallons burned and gph . What I found out was that I get a little better gph at 22 to 28 mph. I can cruise just a comfrotable and faster for the same gph. The boat handles following seas to 2 -3 ft better at a 22-25 then at 16 to18. once its over 4 ft its different. So i found out that I can travel faster for the same mpg . So my speed now has more to do with comfort then mpg. the 27 , because of its lenght , is as comfortable at 25 as a 22 is at 18 on the same seas. I dont have enough time in 25's to make a comparison. I do know from talking to 25 owners that I generally get better mpg then they do. I would like to hear more numbers from them.
T.R. Bauer
New member
Man I have missed a lot.....LOL....
You know, I'd love to get out right now and see what my boat gets. Unfortunately the waters I boat in are forecasted for 17 feet tonight and I think we can now measure September's rainfall in feet..... Seriously.....
I was looking at one of the posts above by Rich saying that he waited for a 1 foot forecast. I have never seen a forecast like that for the Gulf of Alaska. There is such a thing as 1 foot seas???? Man, that is awesome! You'd be waiting a long time here for that forecast. My rule is to not go out if the seas are over 7 feet and wind isn't blowing out of the SE. And I go out all 5 of those days.....LOL....
I envy you go guys for your long season. Mine is done; the boat is in the garage next to the motorhome. Probably time to sharpen ski edges.....
Tim
You know, I'd love to get out right now and see what my boat gets. Unfortunately the waters I boat in are forecasted for 17 feet tonight and I think we can now measure September's rainfall in feet..... Seriously.....
I was looking at one of the posts above by Rich saying that he waited for a 1 foot forecast. I have never seen a forecast like that for the Gulf of Alaska. There is such a thing as 1 foot seas???? Man, that is awesome! You'd be waiting a long time here for that forecast. My rule is to not go out if the seas are over 7 feet and wind isn't blowing out of the SE. And I go out all 5 of those days.....LOL....
I envy you go guys for your long season. Mine is done; the boat is in the garage next to the motorhome. Probably time to sharpen ski edges.....
Tim
Les, thanks for the help with the "speed" calibration. I had looked for that section but did not remember that it was in the sounder window. Will give it a spin.
Guess the important part is to make sure that the tanks have enough gas to get to point B, C and on.
Harvey
SleepyC :moon
Guess the important part is to make sure that the tanks have enough gas to get to point B, C and on.
Harvey
SleepyC :moon
T.R. Bauer":2doi7xch said:
17 feet! Upon seeing those kind of wave heights, I would lose control of my bodily functions. There really is a huge difference between our cruising grounds. We are plagued with short wave period chops, you have bigger waves with longer wave periods, but not always. Reflective waves are not a problem in the East, but as I've seen first hand, it can be a real issue is the PNW. Also, our waters are very shallow. The average of LI Sound is between 90 and 100 feet, but most of the time, we are traveling in very shallow water. Even are tidal variations are less than four feet -- you can hit 12 feet!
For some reason that eludes me, the NOAA can't consistently predict short duration wave height in Long Island Sound; they do a great job, though, in other areas. When they say one foot or less, we know we can hit four feet if the winds come up. Short period waves of four feet are unpleasant even for larger boats. We can navigate OK, but it can be very unpleasant. Most of the time, waves are two feet or less, which is just fine. At three feet, for example, I would rather be traveling in six or seven foot rollers.
Getting back to your weather, people like yourself have to have a lot more knowledge of weather and conditions. You need to exhibit real seamanship and exercise a lot of common sense. My hat is off to you, Tim.
Rich