Fuel flow and economy - Marinaut 215

L

Les Lampman

New member
Hi All,

I have some numbers provided by Rich from the Betty Ann. These numbers were generated with the information given by the engine ECU and the GPS. They were taken over the course of their (almost) 3 week cruise.

The boat was loaded but not to an extreme. Fuel was usually above 1/2, fresh water was usually about 1/2 to full, there was a cooler and a couple of chairs in the cockpit along with mooring items, safety equipment was aboard, and the under galley space fairly full of cookware, food items, and such. Basically, everything needed to spend 3 weeks aboard along with two folks.

2.5 knots ... 1100 rpm ... .32 gph ... 7.8 nmpg ... 9 smpg
5.7 knots ... 1600 rpm ... 1.1 gph ... 5.2 nmpg ... 6 smpg
10.2 knots ... 2600 rpm ... 2.5 gph ... 4.1 nmpg ... 4.7 smpg
13.0 knots ... 3000 rpm ... 3.25 gph ... 4.0 nmpg ... 4.6 smpg
15.2 knots ... 3200 rpm ... 3.50 gph ... 4.3 nmpg ... 5.0 smpg
19.1 knots ... 3500 rpm ... 4.2 gph ... 4.5 nmpg ... 5.2 smpg
21.0 knots ... 3700 rpm ... 4.9 gph ... 4.3 nmph ... 4.9 smpg
23.6 knots ... 4000 rpm ... 5.9 gph ... 4.0 nmpg ... 4.6 smpg
30.0 knots ... 5000 rpm ... 10.0 gph ... 3.0 nmpg ... 3.5 smpg

A lot of folks have asked me for more details so I hope this helps in that effort.
 
Les, we believe, used gas with 10-percent ethanol as we had when these figures were taken. We have also taken readings after using non-ethanol gas procured at Anacortes' fuel dock, with similar results. It seems that 3500 to 3600 rpms is the sweet spot for our Honda Engine, which gives us approximately 5 statute miles per gallon. This is incredible fuel economy, and we believe it is attributable to a combination of many factors: advanced Honda technology, Ben Toland's efficient hull design, Les' focus on weight reduction going to a hand-laid hull, having no bottom coating, making the hull more slippery, and the clean lines of the camperback that affords better airflow (we think) than a stepped design.

As all C-Brats know, careful planning in the way of using currents and/or winds to one's advantage, and maintaining a steady course, will help to ensure one gets high mileage. What's great about the Marinaut/Honda BF115 combination that one gets optimum mileage at low rpm, but at a relatively high rate of speed: approx. 19 knots! In our opinion, which the Honda engine may be more expensive than its competitors, in the long run, its greater fuel economy will more than off set its price in a very short time, dependent upon how many hours one puts on the engine.

Rich
 
For those interested -- I posted a graph of fuel flow, mileage, RPM, and speed information, at approximately 3,500 lbs. total weight, achieved in the Betty Ann's maiden voyage in graphical form in my Photo Album "C-Nile"
 
Desiring to provide an accurate representation of Marinaut 215/Honda BF115 efficiency, I'm refining my results as follows:

On June 14th, my wife and I took a ride on the Connecticut River near Essex, CT. The water was relatively flat, and about 1 hour after ebb tide had started. With two persons on board, I estimate our total weight at 3,580 pounds. We went for 1/4 mile down river, maintaining 3500 RPM, and using our fuel flow meter I calculated we were getting 5.15 MPG. We immediately turned 180 degrees up river, traveled over the same course, and at 3500 RPM (had to increase throttle slightly) I calculated 5.0 MPG.

Fuel flow meter is one thing, the real world is quite another. After topping off our tanks in May, we took 5 trips, traveling 136 miles. Our weight varied from an estimated 3,580 pounds to 4,000 pounds (we took another couple for a 56 mile trip.) We used a total of 29.8 gallons of fuel and this translated into 4.6 statute miles per gallon (see below). We are delighted with the results.

I’ve been seeking advice from Bob Austin, and he won me over to the fact that the fuel flow meter is a valuable tool to instantly determine the most efficient speed for prevailing conditions in real world settings, but that it is not particularly useful for determining overall trip smpg. Mr. Austin likes our overall approach, because it shows the overall average we “...are getting between fill ups, and often involves some displacement speed, some getting on plane, and of course mostly at what ever your cruising speed is. “ Nevertheless, he characterized the results as “impressive.”

This year has been rough thus far for Long Island Sound, and it seemed that every time we went out, we did not time the tides and winds well, which impacted efficiency. It is comforting to us to know that we are getting good mileage from the standpoint of being aware of the true range of our boat. In my opinion, if a person times their trips to sail with the tide, in periods of low wind and flat water, and maintaining the proper trim and throttle settings, 5 mpg is possible to achieve in this boat, but what's the fun of that? We'll settle for overall 4.6 mpg, punch the throttle to make the boat leap out of the hole and just have fun driving it.

OUR LOG
May 19, 2012..........23 miles, seas "6" -> 1’, boat load 3,580 lbs (est)
May 31, 2012.......... 3 miles, seas < 6”, boat load 3,580 lbs (est)
Jun 7, 2012............ 55 miles, seas 6" -> 1’, boat load 4,000 lbs (est)
June 14-15, 2012... 42 miles, seas 6" -> 2', boat load 3,580 lbs (est)
Jun 15, 2012.......... 13 miles, seas 6" -> 1.5', boat load 3,580 lbs (est)
-------------- ---- --------
Total miles........................... 136 miles
Total gallons fuel consumed....29.8
Average miles per gallon----- 4.6

Thanks,

Rich[/b]
 
Hello Bill,

To come up with an average speed is difficult. Here is a good estimate:

Trip 1. 20 miles at 22 mph, 3 miles at 6 mph, seas 6" -> 1’
Trip 2. 3 miles at 6 mph, seas < 6”
Trip 3. 45 miles at 20 mph, 10 miles at 6 mph, seas 6" -> 1’
Trip 4. 29 miles at 17 mph, 13 miles at 6 mph, seas 1’ -> 18”
Trip 5. 11 miles at 17 mph, 2 miles at 6 mph, seas 1’ -> 18”

We have many, extended, slow-no-wake areas. Also, there was a good chop at times, so to run very smoothly, we like to travel at around 17 mph, which is not optimum for efficiency, but very good nevertheless.

Thanks!

Rich
 
This year, as of 8/17/2012, the Betty Ann has travelled a total of 778 miles. We have consumed 173 gallons of fuel at an average cost of $4.60 per gallon to total $793 this year. We are averaging 4.5 statute miles per gallon. Actually, our trips range from a low of 4.4 smpg to a high of 4.6 smpg, and the most important determining factor in fuel economy for us (as for most people) has been wind, tides and wave height. If we planned our trips more carefully, and traveled at optimum speeds, we probably could have reached close to 5 smpg much in the same way as Hyper-milers do, but what's the fun in that? When the rubber hits the road so to speak, it comes down to how many miles did one travel and how much fuel did one consume. I use our Raymarine track mileage counter to determine the number of miles traveled. This method is so reliable to me, that when I filled up yesterday, I predicted we would need 42 gallons of fuel, and it took 41.6. This gives our Marinaut a range of 270 miles.

Incidentally, has anyone noticed how much the price of fuel has been increasing lately? In New England, we paid $4.69 per gallon. Imagine what the cost would be, if you will, if we did not have Marinauts or C-Dory's and got only 2 smpg? Instead of $793 in gas, it would have been $1,789!
 
Marinaut 215 (Betty Ann) YTD Fuel Update as of 9/12/2012:
....Total miles traveled= 963
....Total gallons consumed= 210
....Total fuel cost= $979
....Average miles per gallon= 4.6

Note: My 9/12/2012 fuel fill was 37.9 gallons after 185 miles traveled, which yielded 4.9 mpg. I tried to exercise more careful planning this time around so as to hit slack tide, or following seas, and I paid more attention to achieving optimum fuel flow. What a difference! I believe I'm right in saying that one could hit 5 mpg if it was a priority, but what's the fun in that? It's like hypermiling in an automobile. I'm very happy with the economy of the combination of Marinaut and Honda BF115, particularly now that in my area, the price of gasoline at the marina is $4.899 per gallon.

Rich
 
Rich - what's your average speed during that time? The fuel numbers are impressive but don't mean so much without information about speed.
 
As I have looked at these Marinaut numbers and the verious CD 22 numbers that have appeared on this board as well as watching my own numbers and it is interesting to me that the boats, speaking broadly are getting about 2.5 mpg at a "comfortable" cruising speed on plane, and 4 to 5 gph at off plane speeds in the 8 to 10 mph range. It seems to be the case whether one is running two engines or a single larger engine. Yes, hull shape makes some difference, but I think it pretty much takes the same fuel to move 4000 lbs. or so of boat at speed X without a lot of regard to hull shape.

I also think it is really a stretch for anyone to say that their boat gets X miles per gallon as the winds and water and loading and balance and helmsmanship and currents vary dramatically from hour to hour and day to day and load to load.

Smaller displacement engine (s), smaller boats, good helmsmanship and sea knowledge. That is the key to affordable boating in these times of high fuel costs. Lousy helmsmanship will double the fuel consumption of the best hull and engine combination. Good helmsmanship will double the miles per gallon of the worst combination of hull and engine.

Just my feeling a little philosophical tonight.
 
Harry,

To be honest, I'm not sure how much good or lousy helmsmanship has to do with it. To me it has a lot more to do with how one uses the boat, whether one is in a hurry or not and whether one is most interested in optimizing fuel economy or optimizing a particular kind of fun on the water. Most of my use of both my previous 22 and my current Tomcat has been fishing. When I'm fishing, I'm trying to optimize the fishing fun per unit free time and not fuel mileage. I blast from one potential fishing area to another or run 60 miles offshore for tuna. Once I find my target species, it fish the hell out 'em and then blast back in when I've limited out or run out of daylight. I'm definitely NOT getting the best possible fuel mileage, but I feel I'm getting the best mileage for my $ and free time. I don't consider that lousy helmsmanship, it's just a different goal.

That said, I think your point is that with a little knowledge about the fuel burn characteristics of these boats one can adjust speed to maximize fuel mileage. Without that knowledge, one can easily waste more fuel (especially by running at the "wallowing speed" just before the boat gets on plane).
 
We are in agreement. When I use the term helmanship, I'm really talking about the person who makes all of those decisions about making the mission...fishing, cruising, whatever...the most successful balance of time, speed, water conditions.
 
I just wanted to mention a note about bad helmsmanship. I think it can have a poor effect on fuel mileage. Speeding up and slowing down for no apparent reason, unnessary sharp turns, an improperly loaded boat, motor trim and trim tab settings not in tune with current conditions. Similar to people in hybrid battery equipped cars riding in the passing lanes on an interstate highways doing less than the posted speed limit :love unable to maintain a steady speed of any kind etc.
D.D.
 
Hull design has a lot to do with it. A flat bottomed boat, will do far better than a 26 degree deadrise deep V. (maybe half the mileage in the Deep V).

My father always chided me when I was young--that I was a chinese sailor, trying to break the dragon's back which was following the boat....I learned to steer a straight course--and that is the way you win sailboat races. Almost equal to more miles per gallon....

Helmsmanship also involves anticipating wind shifts and current shifts, wakes etc...

5 miles a gallon seems a stretch--but 2.5 miles a gallon is a bit low for a 4 stroke on a 22--again--the weight does come into effect on identical boats, as well as bottom paint, trim, prop, etc.
 
We have a 23' Venture with a Yamaha 4 stroke 150 and we average around 3 mpg. I rarely have the motor above 4500 rpm. Normally we run between 3500 and 4200 rpm. We usually have a 55 pound dinghy with us and a 2.5 hp Yamaha dink motor and a 65 quart cooler, along with tools, clothes, barbecue, full water tank, roof top air and a Honda EU 2000 generator with five gallons of extra gas for the generator. I don't know if we would be considered loaded heavy but we can't be considered light. I don't factor in if I'm running with the tides or tailwinds. We spin a stainless 3 blade prop 14 1/4 x 17 and use a Permatrim. We start out with 60 gallons of fuel. I would guess a 22 would have to get at least 4 mpg. But we only have a 14 pound anchor. :D
D.D.
 
People,

Regardless of what anyone thinks, the cold hard fact is that I traveled 963 total miles and consumed only 210 gallons of gasoline. I assure you that I was not going hull speed for the majority of those miles. We generally travel between 14 and 23 MPH, except in slow-no-wake zones. Obviously, when we are in slow-no-wake areas, we are going 6 mph, but at slack, and at that speed, we get around 6 mpg as shown on the fuel flow meter. And on those 963 miles: this was measured by the tracks feature of our Raymarine, so not traveling in a straight line does not factor into this discussion. When you think about it, if I under reported mileage, that would be detrimental to favorable miles per gallon rates.

Our crusing grounds are rough. Long Island Sound usually has a good chop, and there are significant tidal flows in our area. These 963 miles were in varied conditions. But really -- does anyone think we bought a speedy cruiser to only go slowly?

I’m in agreement with Bob Austin that to hit 5 mpg on average is a stretch, but we can count on an average of 4.5 mpg (at a boat weight of 3,500 pounds) in varied conditions. It’s all about weight. If I lightened the amount of fuel in the tanks, reduced the amount of water in the bow, carried less gear, and with only me in the boat, I actually think that 5 mpg is possible. We came real close at 4.9 mpg after the last fill-up, and that was with two people in the boat with a full water tank and gas tanks at least 1/2 full. However, with 4 people in the boat, I don’t expect much more then 4.4 mpg, and if conditions were unfavorable, perhaps less then that.

Why are we getting such excellent mileage? In my opinion, the Honda BF115 is one of the most efficient outboard motors ever made. It’s a high torque, low rpm motor. As you all know, Honda makes very efficient engines, but Honda claims this model is 20 percent more efficient then its previous models. Another major factor is the Marinaut itself. She is a light boat for her size. She is not made with a chopper gun -- where you can get uneven distribution of the resin and fiberglass that can lead to higher overall weight. Rather, she is made with hand-laid fiberglass around a closed cell foam core. She is very light. As for hull shapes -- I’m going to stay away from that subject, because I’m not familiar with the hydrodynamics of efficient hull forms. Lastly, our boat is not undercoated. I don’t know the degree of the effect that undercoating has on hull efficiency, but subjectively at least, one would think it would have some affect.

On driving the boat, I agree with those that say that bad helmsmanship has a poor effect on fuel mileage. We're not taking the boat frequently on and off plane. We ride on top of the wave crests in following seas, and make subtle throttle movements -- not major ones. We frequently use our fuel flow meter to determine optimum motor speed settings. Whatever we're doing, it’s obviously working, and 963 miles using 210 gallons of fuel supports that claim.

Thanks,

Rich
 
Will-C":3in5jsn5 said:
I guess that just about wraps it up. The Marinault 215 and the Honda BF 115 are the best boat and motor ever built. AMEN
D.D.
Click to expand...

You say so be it -- I don't. The purpose of publishing my data is intended to provide useful and accurate information to prospective Marinaut buyers, and is not specifically intended for C-Dory owners, although it could help. The Honda BF 115 is one heck of an engine, regardless of whether or not it is on the stern of a C-Dory 22 or Marinaut. Perhaps CD 22 owners who are looking for a new engine can be helped based upon my findings and boat test data? According to Bob Austin, the fuel economy of both boats is similar.

Frankly, when Harry writes that CD 22's, "...speaking broadly are getting about 2.5 mpg at a "comfortable" cruising speed on plane," so as to imply that my numbers are inaccurate -- it gets my hackles up, because I, too, have read posts on this site, and am with Bob Austin when he stated, " 5 miles a gallon seems a stretch--but 2.5 miles a gallon is a bit low for a 4 stroke on a 22--again--the weight does come into effect on identical boats, as well as bottom paint, trim, prop, etc." So Harry: the question you and other CD 22 owners should have is: why is your mileage so low? Is there something wrong with the tuning of the motor? Does the propeller have the right pitch? Is your boat over weight? Do you spend most of your time in a semi-displacement mode? Why is your performance so radically different then other CD 22 owners? It would benefit you greatly, because with the price of fuel today, there would be a huge savings in economy if you even got 3.5 mpg!

There have been a lot of subjective opinions on this site, and admittedly, many have been mine as well, but I've always agreed to listen to the other side, and have not failed to apologize when I wrong. I've tried hard to present an objective approach as much as possible, which is why I worked with Bob Austin to see if my methodology was sound prior to publishing my findings.

So I throw down a challenge to the C-Dory 22 owners on this website. Let your objective voices be heard! What is your overall average miles per gallon in various conditions in terms of total miles travelled for the season and total gallons used? I used an objective approach to generate my figures, using chart plotter mileage data and actual fuel purchased. I'll subjectively wager the CD 22 and Marinaut 215 are similar in fuel economy. But please: don't use fuel flow numbers; Bob Austin schooled me otherwise.

Thanks!

Rich
 
Rich,

I believe you have made some vary valid remarks backed up by hard facts as well as issuing some helpfull opinions/suggestions. Just looking at the design and knowing the weight difference, it would be hard not to think the 215 is going to get better fuel economy than a CD22 even with the same engine.

Jake
 
You know, Jake, I am not trying to convince people to purchase a Marinaut over a C-Dory based upon fuel economy. Honestly, Bob Austin is a boat designer, and he told me off-line that the design of the hull for the Marinaut is slightly less efficient then the C-Dory 22, but that the ride of the Marinaut is slightly better. Indeed, I used to have a CD 16 Crusier, and the ride was rough. If you look at the design of the bow of the CD 16 and the CD 22, it is more rounded. The Marinaut's bow is sharper, and really cuts through the water and travels faster when conditions are rough. Subjectively speaking, I think the main reasons for the excellent fuel economy on the Marinaut are:
1) Honda BF115 efficiency (high torque, low RPM, high technology)
2) shifting fuel weight from the stern to the saddle tanks, placing the water tank in the bow. This reduces drag at the stern
3) lighter overall weight
4) slippery hull that is not bottom coated ( so to compare the CD 22 and my Marinaut fairly, they both would need to be free of bottom coat.
5) using the fuel flow meter to determine optimum efficiency settings. I can't tell you how many times I subjectively think I'm running efficiently until I objectively look at the fuel flow and see how inefficiently I was traveling. Experienced boaters know that an engine, for example, could be running at 4,000 rpm and consuming 6 gallons per hour traveling along at 24 miles per hour, when a mere reduction to 3,500 rpm at 22 miles per hour could result in a drop in fuel flow to 4.8 gallons per hour. Was that extra 2 mph worth it if it is costing 5 more dollars more in fuel per hour? Conversely, one could be running at 3,000 rpm in poor conditions where one is in semi-displacement, and fuel consumption could be going through the roof. So several times per trip, I monitor fuel flow, which has yielded for me excellent results.

Rich
 
Back
Top