Fuel flow and economy - Marinaut 215

hardee · Posted: Mon Sep 17, 2012 2:03 am Post subject:

Les said:

C-Nile · Posted: Mon Sep 17, 2012 2:19 am Post subject:

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

hardee · Posted: Mon Sep 17, 2012 3:00 am Post subject:

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

rogerbum · Posted: Mon Sep 17, 2012 9:53 am Post subject:

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.

C-Nile · Posted: Mon Sep 17, 2012 10:39 am Post subject:

C-Nile · Posted: Mon Sep 17, 2012 10:43 am Post subject:

Will-C

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. Smile

D.D.

Les Lampman · Posted: Mon Sep 17, 2012 11:37 am Post subject:

C-Nile

starcrafttom · Posted: Mon Sep 17, 2012 2:15 pm Post subject:

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 · Posted: Wed Sep 19, 2012 11:49 pm Post subject:

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

hardee · Posted: Thu Sep 20, 2012 2:25 am Post subject:

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

Will-C

I stopped going out when small craft advisories are posted. Too hard to keep my eye on our fuel management screen.
D.D.

C-Nile · Posted: Thu Sep 20, 2012 9:11 am Post subject:

C-Nile