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Conventional 2-stroke fuel mileage comparisons
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ContinuousWave Whaler Moderated Discussion Areas
ContinuousWave: Whaler Performance
Conventional 2-stroke fuel mileage comparisons
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| Author | Topic: Conventional 2-stroke fuel mileage comparisons |
| lhg |
posted 07-31-2003 02:49 PM ET (US) 
Some of us just completed the NC 2003 Rendezvous, hosted by Kingfish, and on the run across the North Channel of Lake Huron, all of us traveled together, same speed and same conditions. Four of the boats left with full tanks, then refilled them on arrival. Here are the interesting results: (we re-filled in Canada so the fuel used is in liters) (distance was about 125 miles) 25 WD Revenge WT, with twin 1991 Mercury 2.5 liter 200 HP V-6's (carbed): 350 liters burned 25 Outrage 25, Armstrong bracket, with twin 1997 Mercury 2.5 liter 200 HP EFI V-6's: 274 liters burned 22 Outrage WD, with twin 1986 Johnson 150 HP V-6's: 238 liters burned 18/19 Outrage II (1992-boat weight 1900 lbs)) with single 1992 Yamaha 150 HP V-6 (carbed): 214 liters burned Clearly, the Mercury EFI technology produced the best economy, considering boat/fuel weight pushed, and engine HP. |
| Bigshot |
posted 07-31-2003 03:37 PM ET (US)
Revenge is much heavier, especially with WD but 20 gallons(approx) is considerably more. I am surprised at the thirsty nature of the 150 Yamaha vs the TWIN 150 crossflow Rude's. |
| BillB |
posted 07-31-2003 03:45 PM ET (US)
I read the thread on the rendezvous, sounds like everyone had a great time.....especially Buckda! I do have a problem (no issue) with your analysis though. I cannot even begin to list the variables in the boats that effect consumption and fail to see how you could work these variables into your calculations in a meaningful way. Could you share your methodology? What you say may well be true, but it is not at all clear based on the "rendezvous" comparison in your post. The claims are more anecdotal in nature than factual. No Merc bashing intended as I now live in fear of that caped crusader Merc_Fan ;)...just an inquiring mind.
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| lhg |
posted 07-31-2003 05:14 PM ET (US)
OK, if we MUST get more technical, here are the wieghts that apply. All of the boats were in close to mint condition, with similar classic Whaler hulls, with two occupants and similar gear for the 5 day trip. Running speeds were in the range of 25-30 MPH. 25 Revenge WD: 4250 25 Outrage/bracket: 3500 22 Outrage WD: 2300 19 Outrage II: 1900 Any way you slice and dice these numbers, multiplication or division, the 200 HP Mercury EFI's got the best fuel mileage, just based on weight alone, and not even considering total HP or top speed capability. The carbed Mercs and Johnsons were close in the middle, and the carbed Yamaha was the worst. And the three larger, twin engined boats, got relatively better mileage than the smaller, single engined boat when figured "per pound" being pushed. That was the biggest surprise. Clearly, a high HP/Weight ratio helps, something you would not expect. It is apparently not true that you save gas by underpowering & working the engine(s) harder. So, like Fox news says, "we report, you decide". All interpretations and opinions welcome. |
| captbone |
posted 07-31-2003 05:31 PM ET (US)
I like that fact that these are real world numbers actually. It gives you a good sense of what you will burn in the real world with one of theses rigs or similiar. I do not think it was really meant to compare. |
| lhg |
posted 07-31-2003 05:37 PM ET (US)
Mistake above, that should be WEIGHT/HP ratio. |
| Jerry Townsend |
posted 07-31-2003 06:37 PM ET (US)
Larry - your information is good and well intended - BUT - for your "tests", the hull shape, wetted surface area and wind facing area are much more important than weight. That is, weight is important when accelerating and coming up to speed - but beyond that, the principal forces the engine/prop has to overcome is resistance - resistance from the water and resistance from the wind. Therefore, in my mind, your test conclusions: "Clearly, the Mercury EFI technology produced the best economy, considering boat/fuel weight pushed, and engine HP. is at best, a bit pre-mature. Clearly, the wetted surface is dependant on the weight (as the weight has to be off-set by the upward forces of the water acting against the wetted surface of the hull), but the hull design also comes into play here. And the wind resistance is also very important. And in both (water and wind) drag forces, the velocity is the predominant parameter. And of course, the condition of the engine and prop as well as the prop design are equally important parameters. Now Larry - I am not Mercury bashing - just relaying Paul Harvey's "The Rest of the Story", Walter Cronkite's "That's the way it is" and as you mention Fox New's "We report - you decide". ------ Jerry/Idaho |
| lhg |
posted 07-31-2003 07:28 PM ET (US)
So we don't, God forbid, get into comparing engine brands, and exposing dirty little secrets, let's just take the 25's, both with twin Mercury 200's, and the 27% more fuel used by the carbed 200's. Some of this additional fuel use is undoubtedly because of the Revenge additional weight. The 1991 200's had only 200 hours on them, while the 1997 EFI's have about 1500 hours on them. Hull is the same. Wetted surface the same? Who knows, but has to be close. Wind resistance? Maybe the fairly aerodynamic Revenge windshield has more resistance than the open Outrage and its center console. Both boats had a radar arch. Both engine lower units are identical, and counter rotating. Both sets of engines were running identical Mercury Laser II 21" pitch props. Water, wind and wave conditions were identical. What's left to be different, other than weights, and efficiency of the engines? Just look at any propeller chart. Weight is always the major component, at all speeds, and for achieving max RPM. I'm not flying completely blind here. Before they were stolen from my boat, I had the same Mercury carbed Mercury 200's on MY boat. I noticed about a 20% mileage improvement after the EFI's were installed. |
| simonmeridew |
posted 07-31-2003 07:49 PM ET (US)
I'm impressed by these figures. I too think we can get some information about real world fuel economy from them; furthermore I think the weight figures and the weight/power ratios are Very Important. I don't know any factual information about hull design and power applications and would like to learn more about it. But it's my observation that an awful lot of horse power is gobbled up keeping a planer hull, especially a deep vee or even a moderately deep vee hull, up on plane. Even my Montauk immediately drops down off plane and screeches to a displacement speed halt when I suddenly cut the power. That tells me a lot of the 70 HP is going towards holding it on plane. Compare that to a sudden loss of power in a displacement hull vessel going slightly less than hull speed. It just coasts and coasts, sometimes enough to scare you in tight quarters. That may even be the situation where an underpowered engine working harder would give better fuel economy. Knock me down, that's how I learn. simonmeridew |
| Peter |
posted 07-31-2003 08:13 PM ET (US)
Interesting report. Converting to MPG, the results are: 25 Revenge WT 1.35 MPG 25 Outrage 1.73 MPG 22 Outrage WD 1.99 MPG 19 Outrage II 2.21 MPG For comparison purposes, my 22 Revenge WT (no WD) powered by a single 225 EFI Yamaha achieves about 3 mpg at 30 mph. I'm interested in knowing what the typical engine speeds were for the twin rigs and single rig at the reported speeds, particularly at 30 mph. I'm guessing that the Yamaha 150 pushing the Outrage II was turning a 17 inch prop and at 30 mph the engine was turning close to 4000 rpm, and in any case well above 3500 rpm. I'm also guessing that the twins are probably turning something less than 3500 rpm to maintain 30 mph. It has been my experience that V6 engines, carbed or EFI, loop charged or cross-flow, anybody's make really start to consume fuel and oil at the 4000 rpm and above level. This might somewhat explain why the 19 Outrage II did not do as well as one might have expected. As another datapoint to compare, my 18 Outrage with the old cross-flow Johnson 150 turning a 21 inch prop would regularly get 3 mpg or better at cruising between 25 and 30 mph. At that speed, the 150 never exceeded 3500 rpm. Weight to power ratio was about 15 lbs per HP. I wonder if the 19 Outrage II had a 200 hp engine (giving it a weight to power ratio below 15) instead of the 150 would it have shown better numbers because the 200 might have been able to turn a larger prop to get the revs down to the magic 3500 rpm and below level at 30 mph. In any case, interesting report. Thanks for sharing it. |
| Peter |
posted 07-31-2003 08:24 PM ET (US)
Ah, now that I know that the Merc's were turning 21 inch propellers, I am going to guess that at 30 mph the Merc's were turning not more than 3300 rpm -- below the magic 3500 rpm threshold. The Johnson 150s were probably spinning 19 inch propellers and were running at or just above 3500. |
| Jerry Townsend |
posted 07-31-2003 09:10 PM ET (US)
Larry - comparing only the two 25s is a much more appropriate comparison - but there are important variables which are not addressed - like the trim angle, which has a major effect and prop rpm. Yes, the trim angle was, in all probability, about the same - but a 1 or 2 degree difference, which one cannot see, makes a big drag difference. And then, the EFI's only had 200 hours on them, while the carbed 200's had around 1500 hours on them. That is a big difference on a 2 stroke engine. Most certainly, the EFI's were in better condition. I would assume that the 1997 EFI's were more efficient than the 1991 carbed engine - by definition. Certainly Mercury engineers are striving to improve the performance of their engines. One can, in essence make this assumption - without your information. Prop rpm is also another important, but unknown parameter - as is the slippage of the prop. et.al. .... In short Larry - I am only saying that drawing firm conclusions based on the information/data you present is perhaps stretching it a bit. Regardless, your information is food for thought - and I'm glad that you guys had a very enjoyable rendezvous. I would give a lot to meet you and Kingfish - but driving 2000 - 3000 miles is a bit more than a lot. ----- Jerry/Idaho |
| Jamie 20 outrage |
posted 07-31-2003 09:53 PM ET (US)
Ihg, thanks for all your effort, locally when we sell a Merc EFI, I downplay the fuel economy because I have yet for a customer to give me a good report. Most of them say it is better, but not by much. The thing I like about the newer EFI is their ruggedness and dependability. Unfortunately, as far as I know they will disappear soon as the 2 cycle EFI dont pass any emission standards. This alone kinda gives an idea about how much fuel is being left behind. |
| lhg |
posted 07-31-2003 09:59 PM ET (US)
Well, I never wanted this thread to get too scientific. But since Jerry is our resident engineer, I knew he would get me in over my head. Jerry, you did get the hours on the engines reversed, however. Peter, at 30 MPH my 25 is turning 3000 RPM, indicating not too much slippage, if conditions are good, which they were on this run. Eagleman, in the Revenge, was indicating about 3300 at same speed, interestingly enough, getting more slippage. Your comments also indicate that an EFI engine does produce better gas mileage, I think. And we know that the DFI engines are even better, with less wasted fuel. Since there has been so much discussion on this site about fuel mileage, etc, I thought these experiences would be of general interest. None of us on this trip made such a big deal out of it. We were having too much fun and differences in fuel economy were not going to ruin it. I think JimH, who also attended, is going to put up some photos of the boating action. |
| Barry |
posted 07-31-2003 10:01 PM ET (US)
My 150's were turning 15x17 SST props and I've got Doel Fins on both engines. Most of the time I was running around 3000 RPM at around 22-25 MPH. Some of the time I was running 3700 RPM at 30-32 MPH. That particular run was almost completely with the wind and the waves. |
| Sal DiMercurio |
posted 07-31-2003 10:12 PM ET (US)
Jerry hit the nail on the head. Some people like to run their engines trimmed in & plates in a semi down position, with throttle positions pushed farther forward then the scenario below, thus using more fuel. This makes for a very flat, rough ride & keeps 90% of the bottom wet using alot of fuel, compared to slight trim & plates up with engines running much easier with less wetted surface. It's a given fact that running large engines at a lower rpm [ with 4" more pitch in the props ] compared to smaller engines having to work much harder & turn more rpms with 4" less pitch to obtain the same speeds. This is the reason I always tell people to power their boats for the maximum hp rating. Yes, that 3,500 majic rpm number is what you need to look at. The 19' boat with a single 17p prop must turn a minimum of 4,000 rpms to keep up with the twins turning 21p props at 3,500 rpms & obtaining 30 mph. As many of you know, i'm way over powered & my engine falls asleep at times running between 3,000 & 3,500 very easy rpms [ 21p prop ]resulting in 5+ mpg, where a 150 hp would need to work much harder & twist minimum of 4,000 - 4,200 rpms to obtain the same speed but goodby fuel economy. The moral of the story is, smaller engines do not give better fuel economy if you have to beat them to death, compared to much larger hp engines that are barely awake giving the same speed at much lower rpms. The above comparisons are not fair because all the boats are different & theres not fair to compare a dfi engines with a carbed, two completely different animals. Sal |
| SuburbanBoy |
posted 08-01-2003 12:01 AM ET (US)
So if the guy who recently asked about re-powering his 18' Outrage is reading, the installation of the 200/225 should prove to be an environmentally sound decision. Scrap the 150 Hp idea and over power for conservation sake! Also consider an adjustable throttle stop. What do the 200 EFI Merc's go for? Are they the 3.0-liter V6 motors? They do seem like a desirable motor. I was quite surprised to hear that they are considered reliable when compared to carbed Merc's. That is nice. I like the idea of a "Real World" comparison. I do it all the time when I travel with my Detroit engineering friends. I am always amazed at the mileage they squeeze out of their V8 pony cars in comparison to my Honda. I generally flog it to keep up and end up with little actual mileage advantage under those sporting conditions. In a Shell economy run I would kill them, but they are too smart to play that game. Plus it always seems as if we are in a hurry. Sometimes, bigger is better, with discretion on the captain’s part helping to keep the shiny side wet. Nice job on the comparo lhg, now, how would the Honda/Yamaha/Merc big 225 4-strokes fair? sub |
| lhg |
posted 08-01-2003 12:42 AM ET (US)
As long as you're trolling, they're too big, fat, ugly, heavy and overpriced to twin power Whaler's old highly efficient Classic 25 full transom Outrages. Now, the soon to be released new Merc in-line 6, supercharged, 250 HP 4-stroke, that's a different story. Another discussion gone to the dogs. We're getting used to it around here lately. That's why so many regulars have left. |
| Peter |
posted 08-01-2003 06:05 AM ET (US)
No question about it Larry, an EFI motor is more fuel efficient than its carbureted cousin. Interesting information on the comparative slippage. I suspect that the bracket design has something to do with it. While I am not very familiar with the Whaler Drive below water, I'm guessing that there is much more below water in the Whaler Drive than the Armstrong bracket. The Whaler Drive is probably acting more like a hull extension rather than a bracket at that speed. If my assumption is correct, there is more drag and less clean water for the motors to bite on. Trim angle is also an important factor. The center of gravity and buoyency should be further forward on the Revenge having a tendency to put more of the bow in the water. If I understand correctly, the 150s were spinning 17 inch propellers, most of the time below the magic engine speed of 3500 rpm. The only unknown is the Yamaha but if my assumptions are correct, it would have been the only engine during the cruise that was operating above 3500 and probably near 4000. Its fuel consumption would be remarkably higher than the others on a per engine basis.
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| Peter |
posted 08-01-2003 08:36 AM ET (US)
Sub, Based on a comparison I did about a year ago between an EFI 2-stroke 225 and a 4-stroke 225 on Pursuit's 2470 walkaround hull (search for it on this site), I suspsect that the 4-stroke equivalents of EFI 2-strokes wouldn't do any better on fuel economy than the comparative EFI 2-stroke. The only place that the 4-stroke did better was at trolling speed. Conclusion that I reached is that 4-strokes just burn more of the fuel rather than dumping it unburnt overboard. |
| SuburbanBoy |
posted 08-01-2003 08:39 AM ET (US)
Larry, I was not trolling. My statements were not a cut at Mercury at all. Sorry if they seemed that way. Is the 200 a 2.5 or 3.0 liter? sub |
| SuburbanBoy |
posted 08-01-2003 08:42 AM ET (US)
As I hit the submit button I saw 2.5 liter in the Larry's first comment, and answered my own question. sub |
| jimh |
posted 08-01-2003 09:26 AM ET (US)
My sense of "fair" is not offended by this comparison, not at all. I think it is informative and quite interesting to compare the fuel consumption of these boats. They all went the same distance at the same speed in the same seas at the same time with the same amount of people and the same amount of gear. There is nothing that is not "fair" about this. How much better could this comparison be? All that is being offered is a report on their fuel consumption and an assertion that the EFI engine had better fuel economy. This is entirely "fair". By the way, my observation of the trim angle is that the 25-Outrage runs with a bit more bow-up trim. The 25-Revenge rides like a PT-Boat, a lot of the keel in the water and the bow rise minimal. |
| Clark Roberts |
posted 08-01-2003 11:43 AM ET (US)
Larry, thanks for taking the time and effort to report this info. Everyone knows that your findings are "empirical" and shouldn't/can't be held to the "scientific method" benchmark! I, too, have noticed that the 2.5L EFI gets better mileage than the similar carb version and even better than the 2.0L Merc carb 150hp (on same boat). Happy Whalin'... Clark.. Spruce Creek Navy PS> Also, I suspect that the human factor of driver habits/tendencies can make a certain difference in identical equipment mileage... blah, blah, blah, blah, blah |
| Dr T |
posted 08-01-2003 12:41 PM ET (US)
Ditto on Clark's PS. I recall a side-by-side comparison of two drivers in the same diesel PU over the same route in an RV magazine(Father and son)where one got 15% better mileage than the other. But it is very interesting food for thought. And the same boat, same driver, different engine comparison is telling. tds |
| Barry |
posted 08-01-2003 12:48 PM ET (US)
The trim on the two 25's was very different, both at rest and at speed. Here are a couple of pictures that illustrate this. These are zoomed in images of long distance shots so the quality is just OK. members.aol.com/bburtensha/nc2003/25front.jpg Obviously on the Revenge, the cap on the front and the Whaler Drive on the rear combine to make it sit and ride much flatter than the Outrage. While this probably makes for a much smoother ride there is more wetted surface. |
| SuburbanBoy |
posted 08-01-2003 01:27 PM ET (US)
I would guess that the boats were trimmed using the set-it and forget-it technique. Driving cars (or trucks) requires many more acceleration periods and other throttle adjustments while underway. This would have a great influence on the consumption rate. For the boats, other than trimming, I get the feeling that they just motored along. Great shots to represent static trim and trim while underway. sub |
| jimh |
posted 08-01-2003 01:36 PM ET (US)
I am not ready to accept that the most significant difference (as in "hit the nail on the head") in the fuel consumption between all these boats was the trim angle. In fact, I don't recall anyone ever mentioning anything with respect to trim angle in any fuel compsumption comparison before. In as much as most of this trip was down wind and with the waves, I don't think trim angle is as important a factor as the basic differences like engine horsepower and induction. In flat water runs, you may find that certain angles of trim are more efficient, but banging around in a following sea of 2-4 footers is probably not a place where trim angle is hugely important in fuel consumption. |
| Bigshot |
posted 08-01-2003 01:50 PM ET (US)
Jim I think you just "hit the nail on the head"(I hope so to put this to rest:) but if you are going with 2-4 waves at the same speed it would make sense that the heavier boat would lose more speed when hitting the backs of waves and hence take more throttle to get going again. The big advantage of EFI is their ability to maitain throttle setting in bigger seas. So if Larry has his set at 3200 in a lighter boat, he may never have to touch the throttle. The heavier Revenge may jerk more and thus need more juice at times. This still does not explain the 19' boat unless he was constantly on and off the gas to keep from getting wet or airborne. |
| lhg |
posted 08-01-2003 02:38 PM ET (US)
Approximately 85% of this run was in calm water, with a tail wind. 15% involved surfing down wind in a 2' sea at most. As Peter's first post shows, the 19 Outrage did get the best fuel mileage, as expected. I think that what is interesting, as total weight, hull length, HP and number of engines increases, the fuel use is nowhere near proportional. It also shows how Whaler's newer, heavier models are not getting the fuel economy of the older, lightweight Classics. I know that my 18 Outrage (33% lighter in weight than this one), with twin 115's, gets about 2.5-2.75 miles/gallon. At 30 MPH, those engines are only turning about 2700 RPM, however. |
| andygere |
posted 08-01-2003 02:43 PM ET (US)
I'm not going to render an opinion; rather I'd like to let the authors of this thread know that it's one of the better ones I've read in quite a while. Good data, good discussion, boat on! |
| Jerry Townsend |
posted 08-01-2003 02:46 PM ET (US)
Larry - sure screwed up when I swapped those engine hours - sorry and my apologies. Hope that is the only mistake I made yesterday. I didn't intend to stir up a hornets nest - just point out a few thoughts. I look forward to seeing the report and pictures of your rendezvous. If I can talk/convince/force my wife into not spending so much time at a nursing home (she likes to help those people, play games with them et.al) I can make some of these events. I would very much enjoy meeting many of you guys. You mentioned that Jimh attended - what about Ray Townsend? --------- Jerry/Idaho |
| Jerry Townsend |
posted 08-01-2003 03:05 PM ET (US)
Larry - you posted your last message as I was typing mine. Your statment: "...It also shows how Whaler's newer, heavier models are not getting the fuel economy of the older, lightweight ..." is basically right on. There is no question, by definition, more weight takes more energy to get up on plane - and once on plane, either more speed at a "shallow" trim angle or a "steeper" trim angle - to maintain that attitude - either of which takes more energy. In other words - more weight requires more energy for similar performance. ------ Jerry/Idaho |
| lhg |
posted 08-01-2003 03:50 PM ET (US)
There are other interesting comparisons here. Looking at the boats powered with 150Hp engines, Barry's 22 with TWIN (and older) 150's only used 10% more fuel than the 19 with a SINGLE 150. To me, that's amazing, and nobody would have guessed it, and I think the difference is probably more accountable to boat/hull configuration than engine MFG. The single Yamaha 150 is newer and loop charged, and the older OMC 150's are cross charged, less efficient. So Barry's lightweight 22WD (only 400 lbs more than the 19) with a much larger (hence easier to plane) hull surface which includes the WD, must be the difference, inspite of the weight of the additional 150 and 300# more fuel. Loading a shorter boat more heavily, like the 19 Outrage II, must make it harder to "push" & plane though the water? Either way, the 22 WD looks like a pretty economical hull to run, even with big twins. There was another boat on this run, Backlash, with a single Yamaha 200, but unfortunately because of different fuel stops, we don't (at least I don't) have the comparison on fuel he used. Since all of us had the conventional 2-stroke technology, there are no comparisons to be made with the DFI's or 4-strokes either. |
| Barry |
posted 08-01-2003 04:17 PM ET (US)
Economical to run WITH the wind and waves at my back. On the ride home heading into that stiff breeze and the waves I bet I burned at least 40 gallons more. |
| Barney |
posted 08-01-2003 08:06 PM ET (US)
I think your boats did very well on fuel consumption. The consumption on the twins was very suprising. I've always heard you burn twice the fuel with twins. Looks like this is not so. Also, compare to my brother-in-law's boat: 22 Foot Glacier Bay catamaran with twin 90 HP Hondas, semi-displacement hull, 4000+ pounds with no fuel, fine riding boat but not fast, averages 2 mpg, and WILL SINK LIKE THE TITANIC. I wish I knew how to bold type that bit and underline it. |
| hooter |
posted 08-02-2003 10:12 AM ET (US)
Larry, Ah'm 'bout as scientific'ly-minded as a Labrador Retriever, and your initial post was all Ah needed to take away some useful comparative information. Thank you, Sir. One thing Ah note gen'rally is that when presented with some information, mah friends with engineer-type minds and job titles tend to look for holes in the data or presentation method like a Schnauzer-dog starin' at a beetle bug in the carpet. They'll do that for hours, if permitted, until the bug plumb gets away under the wall. A Lab, on the other hand, will upon immediate inspection eat the critter and go back to his nap. Interestin' readin', this string, nonetheless. |
| David T |
posted 08-02-2003 02:26 PM ET (US)
I'm confused by the weight listed for the 19 outrage II - I though the dry booat weight was 1200 plus engine fuel people etc., not 1900. |
| Peter |
posted 08-02-2003 08:15 PM ET (US)
The 19 Outrage II has an inner liner that the 18 Outrage doesn't have. It adds about 600 lbs. |
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