fuel economy for 25 Cruiser

[damason]

Will anyone respond about fuel economy at different rpms for a 150 hp 4-stroke on a C-Dory 25 Cruiser. Also if you have a 9.9 hp kicker what is your fuel usage at different rpms.

[Alyssa Jean]

Pat on Daydream and others can probably give a little more detailed info than I, but: I have a Honda 150 and pretty consistently get 4.5 Gal/hour on average. Most all of my boating is in the neighborhood of 16-20 knots, which is in the neighborhood of 4000-4500 RPMs.

[JamesTXSD]

Hi damason,

One of the best things we did to track fuel economy was put in a fuel flow meter. It allows us to trim and adjust RPM to get the best fuel usage. In real world running, we are getting 2.5-3 miles per gallon on average. (Honda 135)

Some time ago, I referenced a chart from BoatTest.com for performance figures for the Honda 150. We found that our figures were not as good as the chart, but we generally run loaded for cruising. Do a search on that site and it will get you in the ballpark.

I was surprised to find out (from the fuel flow meter), that we get better fuel economy at 17-18 knots than we do at 12-13.

HTH

[Doryman]

[Sea Wolf]

[Pat Anderson]

Wind, current, load and your prop all affect this - BUT, I have a Navman which now reports gallons used very close to the amount needed on fill (within a couple of gallons on every tank, given issues with being able to fill to the same level every time) and I use the Garmin GPSMAP76 for its good (and easily accessible) trip computer (Raymarine should take a lesson here). I always divide nautical miles traveled per the trip computer by gallons used. Our 2005 CD25 Cruiser Daydream is almost always loaded to the gills, Honda BF150 main with a BF15 kicker on the transom - the actual calculation shows typical average economy right around 2.5 nautical miles per gallon, occasionally pushing 3.0, sometime down to 2.2 - 2.3. A caution - the Navman instantaneous economy reading is always higher than the actual computed economy, even though the gallons used / remaining is very accurate. I use the Navman instantaneous economy reading not to tell me what economy I am actually getting but just for determining relative economy for various rpms / cruising speeds. The most economical cruise is at about 1,800 rpms, 5 - 6 knots. This is at least twice to three times more economical than planing speeds. The least economical is between 8 or 9 knots and planing speed. Once you get on the plane, for us about 12 knots, the economy is pretty close over the range, although using the Navman economy setting (gallons per hour is not a very useful number unless you can relate that to how far you are going on each gallon) you can see a few "sweet spots" - for us around 3,500 - 3,600 rpms, 13 - 14 knots. The difference though is not dramatic. It really falls off again running at or near WOT, which for us is about 5,500 - 5,600 rpm and around 25 knots. All of this is very much "depending on conditions." I am always skeptical of reports from folks who say that their CD25 goes 30 knots and turns in 4 nautical miles per gallon - my guess is those folks don't really compute their actual economy, because the experience of so many of us is so contrary. It is of course all different for a TC255 because of its more efficient hull design but requiring twin engines.

[Dora~Jean]

I have twin Yamaha 80's and my mileage numbers are essentially identical to Pat's on Daydream. I don't have a fuel flow meter, but I do fill up at the same station and station island to get a consistent fill reading. I average about 2.5 nmpg, 2.2 with 4-5 people and gear, about 3.0 if only 2 of us and seas are relatively smooth to be able to cruise at 15-20 kts.

I suspect though that my boat is considerably lighter than Pat's or most other 25's, I elected to not have the water heater and some other factory gear installed in order to keep my boat light and agile. So the twins probably eat just a touch more gas than a single on an equivalent boat. I plan to install Permatrims on the outboards to see if that improves the efficiency a bit (waiting for the boat-money bowl to fill a bit...).

[Al & Pat Parker]

Hi folks,
I've been wondering about the same subject since we bought our CD-25 in July. At that time our dealer, Mobile East Marine (great folks), had a chart showing the Honda 135-150 on the CD-25. I'm not sure who made the chart, Honda or them. The Yamaha district rep. had similar charts for the Yamaha 150 (which we bought) on other boats, but not on a CD-25. ,
I'll try to attach the chart here:

yes, it looks like it'll go. It's big so makes the screen wide, sorry 'bout that. .
I also have a chart for 2 different props on our boat, on our website, (url in the sig.). Note on that chart, the x-axis is shifted about 500 rpm, look at the table of data. .
I suspect that the Honda chart is a bit optimistic on mpg. I'm a bit dismayed at the 2.5 - 3 mpg no.s that some of you have experienced. We don't have enough time on our to get a good idea, and don't have a log feature on our chart plotter, so just estimate miles. I thought we were seeing 3.5+, we are fairly lightly loaded (still).
as "they" say, "your mileage may vary."

[JamesTXSD]

Well, there's lots about that chart that looks overly optimistic to me... especially that bold line where the conversion from miles per gallon is actually less than nautical miles per gallon. That does not compute. (Obscure "Lost in Space" robot response ). Must be a misprint.

At 5 knots, we are generally seeing a fuel burn of 1.2 gallons per hour, or just a shade over 4nmpg. It goes down from there to about 8 knots, then up again over 12-13 knots. Once on plane, there isn't a great difference (although as stated, 16-18 knots seems to be our "sweet spot" for mpg) until we go over 5000 rpm and then it drops. Loaded, our boat usually tops out around 25 knots at sea level and is getting less than 2.5 nmpg. Lightly loaded with smooth water, we have hit 30 knots a couple times (both gps and paddlewheel)... and it feels kinda twitchy.

And, of course, your mileage may vary.

[thataway]

First we have a Honda 130 and most of our running so far was on Lake Powell--at 3700 feet. Our boat is farily light weight--about 6200 lbs scale weight, plus food and liquids. But when we load, we have full fuel, water, ice chests and food etc. My impression there was that the 130 HP underpowered the boat. We had to get up to about 14 knots before we were on a plane. The graph above also suggests that by the jump from 8.7 knots to 13.4 knots with only a 500 RPM increase in speed. We didn't do anywhere near the 4 miles a gallon--closer to 2.3 miles a gallon at speed--overall we were in the 3 miles a gallon, but that included some running at 5 to 6 knots. On the Pacific Ocean we were getting slightly better (but maybe a little less weight) and in the 2.5 miles per gallon. This is both from the flow meter and fill up to fill up.

If I was to repower I would go with the Suzuki 175. We could not get anywhere near 30 mph with the 130 Honda.

With the Tom Cat we have several thousand miles of data and I feel fairly good with that.

[Bess-C]

We have an '03 with a 130 Honda. The observations by Bob and Pat are close to our experiences. We have always boated at sea level, and the 130 seems adequate at that altitude. We have a top end of about 25-26 knots when fully loaded. I haven't kept accurate records like Pat, but I believe that our fuel economy has averaged around 2 1/2 mpg. I think the 3-4 mpg estimates for a 25 are overly optimistic with a boat loaded for cruising. We generally cruise around 14-16 knots and I use 2 to 2 1/2 mpg for trip planning.

Our Honda 130 has been bullet proof so far, so I'm pleased with it. However, if I was repowering I would probably want a little more power.
Lyle

[Cosmic C]

The Cosmic C has averaged 2.54 standard miles per gallon since new. We have a Honda BF130 and find that quite adequate. Unloaded with one person on board I have done 31 mph (via GPS, no current). The vast majority of our miles have been cruising, fully fueled, watered, holding tanked, and loaded with more than I'd care to admit, and with two people on board. Under these conditions we max at 27 - 28 mph in smooth water. Add even a slight chop and the top speed drops 1 - 2 mph. We have a fuel flow meter on board, and, once on plane, we get max mileage at 18 - 21 mph.

We now have 667.2 hours on the engine, and have travelled 8905 miles, for a lifetime average speed of 13.3 mph. Fuel consumption has been increasing over the last several hundred miles, so I'm wondering if we need some work on the engine.

[bcarli]

Hi
Doesn't the right prop have a lot to do with fuel economy?? So I know this has been discussed a lot but what props are cd-25 people using and do you like them. I have a factory fuel meter and I can at best get about 2.4 miles a gallon. My prop came with my 135 it is S3/14 1/2X15. Les talked about a 4 bladed prop that he liked ( cost over $500 ). My wife and I have been sailors in our past boating life so props and pitch and fuel economy are pretty new to us
thanks

[Sea Wolf]

Bill-

The correct prop for a Cd-25 with a 130/5 or 150 motor has come up in three threads before, as has the 3 vs 4 blade prop question. Look at thi list of topics under the Propellers Section of the Forum.

P.S.: I think you already have the most commonly selected prop for the engine you have!

Joe.

[thataway]

There are a number of other specifications on a prop beside the diameter number of blades and pitch--including rake and cupping. There can be suttle changes which seem to make some minor differences--not only in fuel effeciency, but ability to get on a plane. It also depends on the loading of the boat. Also if you are running at sea level, 3700 or 7500 feet, you will want to drop the pitch of the prop. We usually carry several props--with the primary sea level prop being SS (on the CD 25 it is a 4 blade SS), but the secondary are Aluminum, and a couple of inches pitch lower for the higher altitudes, or very heavy loads. You want to avoid over propping--which might give slightly better fuel economy, but may lug the engine. (not allow it to turn up full RPM). It will help if you find a prop dealer who will let you try out several different props, until you find the best one for your application--and the fuel flow meter will help a good deal there!