posted 01-08-2008 10:18 AM ET (US)            

For every 100 gallons of gas burned by a carbed 200hp 2-Stroke, the following engines of the same HP would have burned about X gallons:

2-Stroke EFI:
E-Tec:
4-Stroke:
Supercharged 4-Stroke:
(any other relavant engine type)

posted 01-08-2008 10:37 AM ET (US)            

Trust me though, I've run the numbers. You have to use your boat a "boatload" of hours (above 300 a season) to justify a new motor based on economics alone. For most people, the benefits of smoke-free, quiet operation, as well as the environmental benefits, factor heavily into the justification.

posted 01-08-2008 12:17 PM ET (US)         

My Mercury service guy at Sundance Marine in Ft Lauderdale, a highly experienced guy on V-6 outboards, tells me I could see about 45% better overall fuel economy by repowering the EFI's with 175 or 200 HP Optimax engines. That is what his experience has been, from the hundreds of owners he has worked with. From what I can tell, and have seen in test reports, Optimax's are just about the fuel economy champions of all outboards, or at least are right up there with the best 4-strokes.

posted 01-08-2008 12:39 PM ET (US)            

That being said, once you have made the change, there is a strange thing that happens-at least to me. I no longer even think about how much gas I am going to use, because it really isn't that much. Granted, I have a smaller boat and motor than you (Yamaha F115), so my numbers are probably more favorable, but I have made 70 mile trips and come back to the gas station for 15 gallons of gas! Also, I am a fan of quiet motors, so that really is a plus to me.

posted 01-08-2008 12:42 PM ET (US)            

Carbed 2-Stroke: 100
Merc EFI 2-Stroke: 90
Optimax: 60
Verado: 60 (from Whaler charts)

posted 01-08-2008 03:13 PM ET (US)            

For example, a 200 HP carbureted/EFI 2-stroke will burn about 2 GPH at 1000 RPM. See www.yamaha-motor.com/assets/products/otb/bulletins/ bulletin_otb_2StrokePerf_OX666_200hp_02-188-CEN-B.pdf . A 200 HP 4-stroke will burn about 1 GPH at idle. See www.yamaha-motor.com/assets/products/otb/bulletins/ bulletin_4stroke_hpv6_gyt3_alm-tourn195sport-f200txr.pdf . That seems like a huge difference in terms of percentage but its only a savings of about $4.00 per hour at idle speed.

Now let's look at cruise. At a 4000 RPM cruise for the 2-stroke, 200, the consumption is about 11 GPH. The 4-stroke won't be able to keep up with the 2-stroke if run at 4000 RPM so you'd have to nudge the throttle up to 4500 RPM. At 4500 RPM, the 200 4-stroke is consuming about 10.5 GPH. So at cruise, you'd be saving about $2.00 per operating hour.

So your hourly savings by going to a 4-stroke ranges between $2 and $4 depending on how fast you operate the motor. So for a typical 50 hour season, your gas cost savings will be in the neighborhood of $100 (if all hours are at cruise) to $200 per year (if all hours are at 1000 RPM). How many 50 hour seasons would you have to operate with this kind of savings before you broke even on the cost of the new motor, rigging labor, taxes, less a trivial trade in amount for a 10 year old motor,etc. the net sum of which is probably well north of $12,000?

My advice...run your old motor until it dies.

posted 01-08-2008 05:18 PM ET (US)            

At least in the Yamaha world this what Yamaha reports:

150 Carb'd ==> www.yamaha-motor.com/assets/products/otb/bulletins/ bulletin_otb_2StrokePerf_HPMidPort_150hp_02-189-CEN-B.pdf

to

posted 01-08-2008 05:33 PM ET (US)            

In 2003 I repowered my 1990 Revenge 22 W.T. with a new 2003 225 Merc Optimax DFI. The Optimax replaced a carbed 1989 Johnson 225.

I never had the numbers, but I always felt that I got about 2.0 nautical miles per gallon on the Johnson. That was at 4,000-4,200 RPM and a bit over 24 knot cruising speed.

With the 2003 Optimax, I now cruise at 3,750 RPM and 29.3 knots and getting about 3.1 nautical miles per gallon (or thereabouts). We made one long run (fully loaded with camping gear, extra fuel, water, 2 POB and running at 3,900 RPM) of about 138 nautical miles burning about 46 gallons of gas = 3.0 nmpg.

In 2003 the Optimax was several thousand dollars cheaper than the 4-stroke engines. From what I know, the Optimax DFI and 4-stroke are close in fuel consumption at crise.

posted 01-08-2008 07:20 PM ET (US)            

Your experience agrees with what the Yamaha customer service told me today when I called. Their customer service rep did not have any data to back up his comments, but he expected I would see about 30% better fuel efficiency from a Yamaha HPDI vs. the engine I have now.

If I cruise with my current engine at 30mph at say 2mpg, that's 15gph. If I put say 50 cruising hours on the boat in a season, that's 750 gallons of gas. Cost: $3000

Annual savings with a new engine: $1000

posted 01-08-2008 07:31 PM ET (US)            

I had to bite the bullet as my old 1989 225 Johnson self destructed. Local mechanic said $8,000 to fix (block, crankshaft, pistons, etc) a 14 year old engine. So spending $13K for new engine was easy (but still painful).

posted 01-08-2008 11:24 PM ET (US)            

Engine Cost Analysis Spreadsheet
http://continuouswave.com/ubb/Forum1/HTML/010848.html

The spreadsheet grew out of a long discussion

New Engine: When to Buy
http://continuouswave.com/ubb/Forum1/HTML/010777.html

The most optimistic prediction of fuel savings is probably about a 50-percent reduction in fuel consumption. The least optimistic is probably about a 30-percent reduction in consumption.

posted 01-09-2008 11:55 AM ET (US)            

For example my friend has a 23 Seacraft that many here have seen. It had twin 130 Yamahas. He repowered with twin 115 Suzuki 4 strokes which weigh about 150lbs more and 30hp less. He lost 1mph at cruise and 1mph at WOT but at cruise he went from 14+gph to 10+. Per tank he was almost 1/2 what the 2s did. Matter of fact his Suzukis are so much more efficient that when he replaced his fuel tank last year he went with a 100gal instead of the 170 in there.

My other thought about this is those who have NOT repowered with a 4s or DFI over a conventional 2s, please keep out of these discussions with your flowcharts and biased manufacturers study charts, etc. You REALLY have no idea what the advantages are but when you do "hop on the bandwagon" I can't wait to hear you eat your words, especially when you say "WHY did I nurse that POS for so long? This engine is HEAVEN". Trust me...you will. I have known about 60 good friends who have gone green and NOT one of them regrets it, most are dumbfounded on how nice it is having something so quiet, efficient, reliable, no more priming bulbs, pumping throttles, sneezing, coughing, shaking, stalling, etc. Just turn the key and vroom!....EVERYTIME. Most have done what you guys suggest, and I have also, which is keep her alive till it blows. You know what though? That is the most frustrating last couple seasons you will experience and the amount of time & $$ wasted trying to keep it alive, would have made for a nice down payment and you would still have a running engine to sell or trade-in instead of a blown POS sittin in your yard.

Lastly...we assume you have a clean, reliable, smooth running 1997 Yamaa 200(not HPDI) that serves all your needs except it is a tad thirsty. I agree with most that you are beter off keeping it until you need/want to repower. Doing it for a couple GPH is not prudent. If you are concerned about your reliability and wish to repower than do so, but don't don't just do it for MPG unless you put a lot of hours a season on her which in that case your 1997 might be close to worn out after 11 years.

posted 01-09-2008 02:52 PM ET (US)            

Jim H. in his summary of the presentation of the financial analysis above suggests an improvement of 30-50 percent.

Jim P's own experience suggests an improvement of over 50 percent.

Nick's friend's experience show an improvement of over 40 percent.

If I were take these figures and apply them to my own Revenge 25 Walk Through with twin carburetor equipped two stroke 150 outboard motors, which will get 2.3 MPG, I am lead to believe I could see 3 MPG to 3.5 MPG if I were to repower with four stoke power? I don't think so.

posted 01-09-2008 03:01 PM ET (US)            

Sirotis' original quiry was: Approximately how much less fuel would I burn by going from a carburetor two-cycle versus a new four-cycle outboard?

So I answered the question and I did it in the context of a Yamaha 200 HP 4-stroke because

1) Sirotis owns a 200 Yamaha,

2) unlike Mercury, Yamaha has a wealth of performance information about its products including products now obsolete like the EFI Ox66 200 which has the same consumption profile as a carbureted 200, and

3) if Sirotis repowered, it would likely be with a Yamaha 4-stroke so he could reuse his controls and SAVE money, which is the underlying basis for Sirotis' inquiry.

But to alleviate whatever 4-stroke paranoia you may be experiencing, if Sirotis repowered with a Yamaha because it would require the least rerigging effort and expense, the cost savings would be even less than predicted with the 4-stroke because the HPDI system is not nearly as fuel efficient in the idle speed range as a 4-stroke or the DFI 2-strokes that use stratified charging. If you have any doubts about this, then I suggest you compare the 1000 RPM number from

www.yamaha-motor.com/assets/products/otb/bulletins/ bulletin_otb_2StrokePerf_HPDI_200hp_02-200-COB-B.pdf

to this

www.evinrude.com/NR/rdonlyres/67F35EC8-EFB4-4B38-BD2C-E679A96A7441/0/ PE451.pdf

Since you are and have been the resident Mercury sales man here for quite some time, Larry, I'll leave it to you to contribute your own useful Mercury materials rather than the "bias manufacturers study charts" which contain only self promoting conclusions and none of the underlying facts that led them to such.

Oh yea, unlike you, Larry, I actually own and operate two DFI 2-strokes that run with the stratified charge mode each of which burn 0.3 GPH at idle and about 0.6 GPH at 1000 RPM per the Navman F3100 (have you got a fuel management computer on your boat?). Unlike you, I've actually owned and operated a carb'd 2-stroke Yamaha. Unlike you, I've actually owned and operated a Yamaha EFI Ox66 2-stroke and have observed the same fuel consumption rates Yamaha sets forth in its published reports.

posted 01-09-2008 03:11 PM ET (US)         

First of all those doggy old Merc 150's of yours are giving remarkably good mileage at 2.3 MPG on a boat that size. JimH's smaller, and much lighter 22 Revenge with 225 single OMC only gets 1.75 MPG. My 25 with the 200EFI's only gets 2.0 MPG.

If you look at Cetacesa Page 78 you will see JimH and I, and ladies + driver, riding in BW 240 Outrage, dry hull weight of 4400#, heavier hull and deeper Vee than your Revenge, with twin 150 Opti's running 19" Vengeance props. The boat was running 51 MPH on GPS and registering 3.1 MPG wide open. So your figures may be OK, or close.

posted 01-09-2008 03:26 PM ET (US)            

I am sorry, you are wrong. The Outrage 240 you were in was not getting 3.1 MPG at WOT. Perhaps you were looking at the readout of just one of the two engines which would suggest the boat was getting 1.55 MPG at WOT which is consistent with Whaler's performance data of that boat and motor combination. http://www.whaler.com/rec/pdfs/performance/13.pdf

But all of these is misses the point. I would like to see a [b]four stroke[/] power option that offers me 3-3.5 MPG on my boat. I don't think the Verado 150s are going to be the answer as Whaler's performance data for the aforementioned Outrage 240 with Verado 150s show that it actually gets worse fuel mileage than the two stroke outboards.

posted 01-09-2008 06:17 PM ET (US)         

Looking at that report, I note that my actual experience in that boat was slighly better than Whaler indicates. I know I saw the 51.x MPH top end, and I also know I saw the Smartcraft readout on combined engine fuel economy of 3.1 MPG. But looking at the Whaler figures at 3500/30 MPH cruise, I see 2.86 MPG, so the economy figure I saw must have also been at that cruise. Maybe Jimh can verify.

posted 01-10-2008 12:00 AM ET (US)            

--air temperature (colder is better)
--water temperature (colder is better)
--load on the boat (lighter is better)
--propeller in use (more pitch is better)
--wind and wave conditions (tail wind and just a light chop is best)

and this is really where the engine and boat operate most efficiently. At any other speed range, at idle, slower, or faster, the MPG declines.

On a long term basis I have collected some data at:

http://continuouswave.com/whaler/reference/propellerWDSingle. html#seasonalData

which shows that 1.7 to 1.8 MPG average is about right, but that includes a lot of low speed operation where the motor is very wasteful of fuel. What I have learned, however, is that the total fuel economy is most influenced by the fuel economy where most of the fuel is burned. Because so much more fuel is burned at cruise than at idle, the fuel economy differential at cruise will have the biggest impact on the total fuel economy average. This means that a new engine will probably be better at cruise, of course, but it won't be twice as good, that is, it won't cut the fuel in half. I'd say more like a 30-percent improvement. So if I get 2-MPG now, I'd be happy with 2.6-MPG with the new motor, and anything more would be a bonus.

At lower speeds the difference will be much greater. At idle, where now I get sometimes a fuel economy of a terrible 1.5-MPG, I would probably get 4-MPG or higher. The irony of this, and not very clear to most people, is that the better the fuel economy at idle, the less it effects the average fuel economy, even if you spend a lot of time at idle. I explain this in my reference article, but it does not seem to have made much impact on readers.

posted 01-10-2008 12:21 AM ET (US)            

Let me clarify my recollection. The OUTRAGE with twin OptiMax and 3.1-MPG was at a cruise speed, albeit a fast one, but not at WOT. Probably at 28-MPH to 30-MPH. That I do seem to recall with some certainty.

Heck, if I could get 3.1-MPG at cruise on my boat, well, I'd do 50-percent more boating!

posted 01-10-2008 12:52 AM ET (US)            

If Tom says he gets 2.3-MPG at cruise now with his old two-cycle motors, and if we apply the 30-percent improvement factor, he will have to get 3-MPG with the new motors. It may be hard to find a set up where he is going to get 3-MPG from a pair of new motors at cruise.

Like Tom, I have looked at fuel consumption rates for modern motors in applications which I think are reasonably comparable to my current boat and motor situation, and, as Tom Clark has suggested, it is hard to find examples where you can see a stunning improvement in MPG at optimum cruise speed.

In my case I figure my reliable cruise is about 2.0 to 2.1-MPG, so I just have to get up to 2.6 to 2.7-MPG to make a 30-percent improvement. When I look at test results for single 225-HP motors spinning 17-inch propellers on fairly big 22 to 24 foot boats, I don't see too many numbers better than 2.7-MPG.

Here is a typical report, a 225-HP E-TEC on a big 22-footer:

http://www.evinrude.com/NR/rdonlyres/ 586B65F8-5917-4131-B887-581555C8D507/0/PE444.pdf

The fuel economy at cruise is 2.7-MPG. I use that as a guideline to what I would probably get. That's a 30-percent improvement at cruise. I doubt you can do much better.

Now that same report shows about 7-MPG at idle or no-wake speed, which is vastly better than my current 1.5 to 1.7-MPG. That is where I will pick a lot of improvement.

posted 01-10-2008 01:33 AM ET (US)            

And this Mako 232 CC also with a 225 4 stroke that gets 3 MPG cruise.
http://www.honda-marine.com/pdfs/ptMAKO%203.pdf

And a 23.5 foot walkaround with a 225 4 stroke that gets 3.1 MPG cruise.
http://www.honda-marine.com/pdfs/ptTRITON%201.pdf

posted 01-10-2008 08:24 AM ET (US)            

Traditional 2 stroke WOT fuel consumption (gph) is hp/7.2
4 stroke (or 2 stroke dfi) WOT fuel consumption (gph) is hp/10.8

For example, if we have 100hp 4 stroke and 2 stroke engines. WOT gas consumption is around:
4 stroke burns: 100/10.8 = 9.3gph
2 stroke burns: 100/7.2 = 13.9gph

When running cruise speed, the difference between 4 and stroke is much smaller, but at idle the difference is much bigger.

These figures are not scientific accurate, more like rough estimates.

posted 01-10-2008 08:44 AM ET (US)            

Using Jim's data for the 4000 RPM point for the 15 x 17 SST propeller, I calculate the consumption rate for his carb'd motor to be about 12.6 GPH. If it were an Evinrude DFI 2-stroke, he would see that consumption rate drop to about 10.5 to 11 GPH at the same 29 MPH or about 2.75 MPG. Still not quite 3 MPG at cruise but about a 20 percent improvement at 29 MPH.

With a modern DFI 2-stroke or 4-stroke, the significant improvement in fuel economy over a carb'd 2-stroke comes in the off-plane, no wake speeds. For example, my twin 225 Fichts at 1000 RPM consume approximately 1.5 to 2 GPH combined pushing the 27 Whaler WD 6 MPH in the channel yielding about 3 to 4 MPG depending on the current and wind. The carb'd versions of those motors, which Jim has, would burn approximately 2.5 to 3 GPH each or about 5 to 6 GPH combined at the same RPM pushing the boat the same speed yielding about 1 MPG.

Generally speaking, with carb'd 2-strokes, the MPG at off-plane, no wake speed is worse than the MPG on-plane at cruise speed. The opposite is so with DFI 2-strokes or 4-strokes, the off-plane, no wake MPG is better than the on-plane MPG.

Tom would certainly see an improvement in fuel economy switching out his 150 HP Mercury 2-strokes for any of the 150 HP 4-strokes but not knowing the consumption rate for the carb'd Mercury 150s, its difficult to tell how much of an improvement. Whatever it was, most of it would come at the no-wake speeds.

posted 01-10-2008 09:15 AM ET (US)            

Several posters far more knowledgeable than I have given you some estimations on the percentage that you will save on fuel economy.

I see that you are an engineer like several of my best friends. Most of my engineer friends are "very" analytical when it comes to making purchase decisions about their boats (e.g. cost vs benefit etc.).

Based upon the fact that you currently own a 97 Yamaha 200 hp, I am going to assume that you own it outright "free and clear". For the heck of it, I went on Ed's Marine (website)to check the prices of 3 different new 200 hp o/b's. Suzuki 4-stroke 200hp ($10K), E-Tech 200 hp ($14.5K), Merc. Opti 200 hp ($12.8K).

Let's say you go with the least expensive at $10K. Let's say you use 30% less fuel with every fill up on the 4 stroke on a 100 gallon tank. If gas is $4.00 a gallon, you would burn $120.00 less in fuel with the 4-stroke per 100 gallon tank. You would break even after the 83rd time that you bought 100 gallons of gas.

So, if it's all about cost analysis to you, you should certainly consider how many time per year that you fill up your tank. If you purchased 100 gallons of gas 1 time per month, it would take almost 7 years to break even.

My brief 2 cents on 2-stroke vs 4-stroke. I owned a 1999 200 hp Merc 2 stroke for 7 years and for the past 2 years have owned twin 225 2004 Merc 4-strokes. This is just based on my experience with my motors, others certainly may vary.

2-stroke had better hole shot and was a fast running engine. However, it was loud, smoky and didn’t get great fuel economy. I never knew how much the difference (noise and smoke) was until I went to 4 strokes.

4-strokes, less of a hole shot. Other than that, I have been very happy. My twins are so quiet that on several occassions, when a dock master has been casting off my lines for me at different marinas, they would say: “OK Capt. You can start your motors”. I would reply: “they are already on”. No smoke and very good fuel economy. Great for long range trips on the water. You can have a conversation while running at higher speeds without having to screami at the person standing right next to you.

Good luck with your decision.

Brian

posted 01-10-2008 11:14 AM ET (US)            

quote:

---

Tom would certainly see an improvement in fuel economy switching out his 150 HP Mercury 2-strokes for any of the 150 HP 4-strokes but not knowing the consumption rate for the carb'd Mercury 150s, its difficult to tell how much of an improvement

---

I can imagine seeing an improvement, but I am looking for the alleged 30-50 percent improvement that is still being claimed possible when going from old carb'd two strokes to modern four strokes.

It is not an improvement at idle speed that I seek; I spend very little time idling my motors and when I do, as in a Marina, I often am running only one motor. I am looking for real fuel savings, i.e. at cruise speeds.

Would anybody care to make a prediction of what I could realistically expect?

For the record I have measured and calculated my fuel consumption very carefully using my calibrated FloScan TwinScan fuel flow meter/totalizer. I have also verified my 2.3 MPG fuel mileage over a four hour trip between Seattle and Neah Bay last summer. Fuel consumption at optimal cruise is 14.6 gallons/hour. Fuel consumption at WOT is 31 gallons/hour.

posted 01-10-2008 11:39 AM ET (US)            

Now you are on to my dirty little secret: optimal cruise speed is 33.8 MPH and 47.2 at WOT.

The fuel mileage verifying trip last summer was made starting with full fuel and oil, three adults, downriggers, cannon balls, god knows how many tackle boxes, three full coolers, duffle bags, camera bags, full canvas, etc. We were loaded for five days of fishing. I estimate our starting weight at 6500-7000 pounds, based on Whaler published weight of the Revenge 25 Walk Through of 4000 pounds.

posted 01-10-2008 01:23 PM ET (US)            

www.yamaha-motor.com/assets/products/otb/bulletins/ bulletin_4stroke_hpv6_rel_pur-c250cc-t-f150txr.pdf

posted 01-10-2008 01:42 PM ET (US)            

Whaler at least has some data. The current production Whaler closest to my Revenge 25 Walk Through is the Conquest 255. Here is the test data for that boat:

http://www.whaler.com/rec/pdfs/performance/14.pdf

Weight as tested is 6812 pounds which comparable to my own, but look at the fuel mileage! Those Verados only get 2.29 MPG and the top speed is a mere 43.6 MPH.

posted 01-10-2008 04:05 PM ET (US)            

That is a thought and one I have thought of myself with the anticipated Yamaha F300.

Unfortunately, Whaler has no data for the Conquest 255 with the Verado 300. They do have test data for the Verado 275 however and it does get better fuel mileage than the twin Verado 150s, but at only 2.45 MPG is a pretty marginal improvement and the top speed is no better at a rather sluggish 43.4 MPH.

posted 01-10-2008 08:51 PM ET (US)            

And a 24' Carolina Skiff w/ twin 150 4 strokes that only weighs 5700 lbs loaded but gets 3.44 MPG cruise and 51 MPH top speed.
http://www.honda-marine.com/pdfs/ptCAROLINA_SKIFF_4.pdf

posted 01-10-2008 11:33 PM ET (US)            

When I look for comparable results with other hulls and motors, I look for the same horsepower and the same top speed range. I had not thought about computing the HULL FACTOR from the test data, but that is a good method. You want to compare to a hull which is similar to your hull.

Tom's situation may be a bit harder to optimize because of the twin engine configuration. If he goes to twin four-cycle engines, he will add some weight. The extra weight has to be overcome, and that takes a little off the top of any gain in fuel economy from the motor.

posted 01-10-2008 11:49 PM ET (US)            

Good on you for finding something that might theoretically provide fuel mileage for my boat that is 30 percent better than what I get now. Of your two examples, only the McKee 24 Freedom is a good comp, and only if we take the "loaded weight" to mean "weight as tested". Note the hull weight is listed as 3600 pounds, 400 pounds less than my boat, but perhaps the difference is the added engine weight itself, as Jim points out.

Also note that these twin Honda BF150s make their best mileage at only 23.6 MPH which would be a HUGE improvement for my boat.

Jim,

Yes, I find the best fuel mileage for my motors comes when running them at 4000-4200 RPM. That is their sweet spot. The reason I mentioned my "dirty little secret" above is that in order to achieve 2.3 MPH in my boat, it has to be run at this speed, which is VERY uncomfortable in anything but very calm conditions. In anything more than a one foot chop, I have to slow down to avoid getting beat up. This is a large part of my love/hate relationship with these motors; sure they run great but only if you go fast.

posted 01-11-2008 12:03 AM ET (US)            

http://www.suzukimarine.com/boat_builders/boat_tests/key_west_boats_inc/ key_west_268_cc/df300/

This boat, which is clearly a larger (though perhaps not heavier) is getting 3.3 MPH at 21.5 MPH and 3.1 MPG at 25.1 MPH!

posted 01-11-2008 01:47 PM ET (US)            

Many here claim 3 to 3.5 MPG with a carbed 150 HP 2 stroke on an Outrage 18. I don't think it would be too far fetched to see 4.5 to 5.5 MPG with a 150 4 stroke or DFI on a 18 Outrage.

posted 01-11-2008 03:06 PM ET (US)            

If so, I think it is possible that a single 250+ 4-stroke (or even one of those "gas guzzling" DFI 2-strokes) could get you very close to, if not in, the 3 MPG cruise promised land since you don't have a Whaler Drive.

That Pro-Line report looks very impressive, almost seems too good to be true. Between the two reports it seems that if you keep the Suzuki 300 at 4000 RPM or below, it has very good fuel consumption numbers. I'm guessing that 4000 RPM is probably the point where the variable valve timing (VVT) changes modes in some significant way.

Perry -- Regarding the 18 Outrage, I think this is fairly representative of what you'd see for gas mileage with a 150 4-stroke or DFI 2-stroke. www.yamaha-motor.com/assets/products/otb/bulletins/ bulletin_otb_4StrokePerf_HPV6_150hp_03-16-EDG-C.pdf .
At 30 MPH, the 2-stroke 150 is probably burning 8 GPH versus the 6.5 GPH. We'll know better this Summer because I'm going to put a fuel flow gauge on my 18 Outrage.

posted 01-11-2008 04:22 PM ET (US)            

According to this thread started by Buckda, he also saw around 3 MPG with his old 150 Mercury at cruise and others agree that it is a normal fuel consumption rate for his set-up.

http://continuouswave.com/ubb/Forum4/HTML/003812.html

posted 01-11-2008 05:25 PM ET (US)            

The RPM versus speed numbers reported for the carb'd Yamaha 150 2-stroke in this report

www.yamaha-motor.com/assets/products/otb/bulletins/ bulletin_2stroke_hpmidport_sws_ang-204wale-150txrc.pdf

are not that far off of what I see with my Johnson 150 on the 18 Outrage. I cruise 30 MPH at 3500 RPM. I think the fuel burn rates per RPM are similar given that my Johnson also has a 5500 RPM redline. So my estimate of 8 GPH at 30 MPH for my Johnson 150 is probably not far off the mark, could be a bit high. The 150 4-stroke, or DFI 2-stroke, will use about 1.5 GPH less at cruise than the carb'd 2-stroke.

posted 01-11-2008 07:31 PM ET (US)            

The link you provided to the performance test of the 18.6' Edgewater showed the F150 burned arounf 6.5 GPH at 30 MPH but it also only burnded 3.5 GPH at 20 MPH.

posted 01-12-2008 01:12 AM ET (US)            

In truth, I would prefer that my boat achieved it optimal fuel mileage between 25 and 30 MPH. That would make it a MUCH more comfortable boat to cruise in.

Carson,

There is no way that Dave "Gambler" got only 3 MPG when it had its 150 Mercury two stroke on it. That is exactly the motor I have on my Revenge x two. My boat is more than twice the boat of an Outrage 18 and uses the same pitch propeller and is capable of the same speeds. i would expect it to be able to achieve at least twice the fuel mileage if not more. That would be 4.6 MPG if not 5 MPG or more.

For a four stroke to best that by 30-50 percent would really be something, and i do not believe that is going to happen.

posted 01-12-2008 02:39 AM ET (US)            

I also searched Continuous Wave and found user vdbgroup stated he got 3-3.5 MPG cruise on his Outrage 18 with Yamaha 150 2 stroke.

And user myakka stated his Outrage 18 with Mercury 150 2 stroke got 3.45 MPG cruise.

So it appears 3-3.5 MPG cruise with a 150 carbed 2 stroke on an Outrage 18 is the norm.

posted 01-12-2008 09:23 AM ET (US)            

quote:

---

I am perplexed by the low fuel consumption of the carbed 2 strokes on your Revenge. Somehow you really have them sipping the gas.

---

I will email two Excel files to you and Tom Clark with this data and a comparison of all of the Whaler Outrage 210 engine test data graphed. Some interesting ideas came to me looking at the graphs.

posted 01-12-2008 11:21 AM ET (US)            

OK, I certainly am not questioning the veracity of Dave's data but we are starting to cloud the discussion by mixing up two very different ideas of fuel economy. There is fuel economy at the cruise speed one usually runs one's boat, and then there is optimal fuel economy. Let's not mix them up.

My boats gets its best fuel economy, 2.3 MPG at 34 MPH. At 25 MPH my motors burn about 6.5 gallons per hour I believe (I don't have my data sheets in front of me this morning.) I would like to see a full test report of speeds (measured and averaged from two directions), RPM and fuel consumption rates for Gambler when it had its Mercury 150.

I suspect we will see that the best fuel economy for that motor was when it was running over 4000 RPM and at that engine speed the boat would have to be going well into the 30s which is not a comfortable cruise in an Outrage 18 in anything but baby-butt smooth water.

When I bought my Revenge I was a little slow to figure this all out. It was my brother who pointed out that we could accelerate from 25 MPH to 35 MPH and the fuel flow meter hardy indicated any increase in fuel consumption. Only after running numerous propeller tests with different props did I really start to pay attention to the fuel economy figures as well. It also went against my long held belief that an outboard powered boat would get its best fuel economy at minimum planing speed when the thing was just loafing along. THIS IS NOT SO.

But the real world is full of wind and waves on the water and the reality is that we may not want to, or be able to, run our boats as fast as necessary to achieve the very best fuel economy. This is where we are getting many of the anecdotal reports of fuel economy cited above. And I want to emphasize that I think it is good to discuss the fuel economy our boats get the way we actually use them because that is more realistic.

But for the purposes of comparisons, let us not mix the two types of fuel economy up. In a recent too-long discussion we threw out all manner of fuel economy data from tests of different outboard motors and boats. All of these data points were OPTIMAL fuel economy, not necessarily the fuel economy one would see if they owned the boat and ran it at a different speed.

There is also the fuel economy that is measured against the length of a trip against the fuel burned. In this case, idling, trolling low sped, no wake speed and cruising speed are all mixed into the calculation. This is usually going to yield a different result.

The confirmed 2.3 MPG I saw last summer on my trip to Neah Bay was, in fact, a total trip measurement but one in which I was deliberately trying to see if I could achieve the fuel mileage I had been measuring with my FloScan. It included the start and warm up at the ramp and the idling out of the marina. The total time included three brief stops to urinate and there were two area where the water was way too rough to maintain my fast cruise speed. In spite of all that, I covered 200 NM with 60 gallons of gasoline.

posted 01-12-2008 11:37 AM ET (US)            

quote:

---

I am perplexed by the low fuel consumption of the carbed 2 strokes on your Revenge. Somehow you really have them sipping the gas. I bet your good fuel economy is related in part to the fact that you have your motors in good running condition and mounted at the proper height and your props are dialed in just right.

---

Carson,

When I take the Revenge out for a spin and look at my fuel totalizer, or fill the tank of the gas station, I do not think of my motors as "sipping" the gas. That is why I have been so keen to try to maximize the fuel economy if I can.

When I bought the Revenge 25 from the original owner it had Mercury aluminum three blade propellers. It appeared that it was always so equipped. The motors had also been mounted as low as they could be. The boat was capable of 45 MPH and got 2.0 MPG at best. The performance of the boat was not bad but once I started fooling with the props (mostly to see if I could find a way to claim bragging rights of a 50 MPH boat) I came to realize in a way I never had before through the ownership of over a dozen boats, that a propeller can have a really significant impact on the performance of a boat. Not only is top speed affected, but acceleration grip, and fuel economy as well.

This is where I started to get really curious about propellers two years ago and I have had a lot of fun and learned a great deal since then. It is an area of interest I am trying share with others now.

posted 01-12-2008 01:32 PM ET (US)            

I honestly do not understand your question. Optimal fuel economy is achieved at a speed and RPM where the most ground is covered for the least fuel consumed. On my boat this occurs around 35 MPH. Best fuel economy is an objective measurement. Prefered cruising speed is a subjective choice. The two have little to do with each other.

I would prefer to have a power source that achieves its optimal fuel economy at a slower speed because here on Puget Sound the boat is more comfortable to be in at 25-30 MPH.

Fuel economy depends on the motor, in this case the motor is most efficient at around 4000-4200 RPM and I think this is typical, is it not?

The speed at which I cruise is dependent on the boat and the condition in which it runs. If it is smooth or rippled my boat is great at 35 MPH or more. Unfortunately, here on Puget Sound we have a lot of tidal current, wind and boat traffic, both commercial and recreational. It often is choppy and sloppy with waves coming from many directions at once. A Revenge 25 is not a smooth ride at 35 MPH in those conditions.

posted 01-12-2008 02:00 PM ET (US)            

When I said your motors sip gas I meant relatively speaking.

posted 01-12-2008 03:08 PM ET (US)            

So in trying to "size" the 2-stroke power for a classic Whaler V hull so the "maximum" efficiency coincided with the comfort zone, I've always tried to select motors capable pushing the boat in the 25 to 30 MPH zone while turning 3500 to 4000 RPM. So, if running lower than 3500 at 30 MPH, for example, I think there could be a case that the boat has too much motor and if running much higher than 4000 RPM at 30, not enough motor. Sort of fits with your notion of "the boat might really be happier with less power". Does that make any sense?

posted 01-12-2008 03:17 PM ET (US)            

I have provided one data point for my boat. Maybe it is an anomaly. I can back up my data with solid documentation. I would like to see some other well documented data points showing where the best fuel economy is with different motors.

Peter - Let's start with your current Outrage 18 with its Johnson 150 HP motor. Do you have some good Speed-RPM-Fuel Consumption data taken throughout the motors RPM range? What other boats have you owned that also have good data to go with them?

Dave Buckalew (buckda) - Could you please join us here and share your data from before and after repowering your Outrage 18?

posted 01-12-2008 03:35 PM ET (US)            

188.64 miles
7 hours 8 minutes run time
26.46 mph average speed
31.25 gallons of fuel burned.
6.04 miles per gallon
$123.36 cost of fuel
$3.95 cost per gallon of gas. (Marina fuel was $4.20/gallon)
I ran mostly at 4600 rpm or around 29-31 mph.

http://continuouswave.com/ubb/Forum1/HTML/015291.html

Here's data on another trip with my 2004 90 carbureated Mercury/Yamaha.

1) 99.38 miles round trip
2) Average speed 21.38 mph
3) Trip time 4 hours 39 minutes. (Does not include stop time.)
4) Fuel used 19.02 gallons
5) River current speed 1.7 mph.
6) Estimated running at 4,200 rpm.
7) 5.23 miles per gallon.
8) Wind speed less than 5 mph.
9) Temperature 63 degrees.

Here's a trip with the FOURSTROKE.

1) Average speed 19.6 miles per hour.
2) Max speed 45.56
3) Time running above 5 mph, 6 hours 22 minutes.
4) Trip distance, 124.77 miles.
5) Fuel consumed 20.50 gallons
6) 6.08 miles per gallon.

http://continuouswave.com/ubb/Forum7/HTML/000823.html

I can probably get 8 mpg if I average 20 mph on a long trip.

posted 01-12-2008 03:39 PM ET (US)            

http://continuouswave.com/ubb/Forum8/HTML/002469.html

If the water is flat I can get 7-8 mpg going slow.

posted 01-12-2008 03:59 PM ET (US)            

Do you the data showing the fuel consumption rate and speed at different RPMs between planing speed and WOT?

posted 01-12-2008 04:03 PM ET (US)            

http://continuouswave.com/ubb/Forum7/HTML/000797.html

Trip data with 90 FOURSTROKE

posted 01-12-2008 04:07 PM ET (US)            

http://www.whaler.com/rec/pdfs/performance/6.pdf

posted 01-12-2008 04:15 PM ET (US)            

So I will enter the data from a prop test on my boat as a reference. I used a calibrated Navman 3100 Fuel and it was set on MPG. Speed measured by Garmin GPS. Performance of my BF135 Should be identical to a BF150 up until 4200 RPM when the BF150 benifits from VTEC.

Boat:......190 Nantucket w/T-Top
Prop:......Solas 4 X 14.25 X 17 HR Titan
Fuel:......56 Gallons
Air temp:..85 degrees
Water/wind:Calm

RPM.........MPH..........MPG
2000........7.5..........5.5
2500........8.5..........6.5
3000........12.1.........4.2
3500........21.7.........6.5
4000........27.3.........6.1
4500........32.1.........4.7
5000........36.2.........3.7
5500........40.1.........3.3
6000........43.2.........3.2
6100........44.1.........3.2

Minimum planning speed:.18 MPH
Time to plane:..........4.8 seconds
0-30 MPH:...............8.9 seconds

posted 01-12-2008 06:56 PM ET (US)            

quote:

---

My 1996 Outrage 21 with 1998 200 carb Mercury runS similar to Tom Clark's. Maximum MPG is between 3800-4400 RPM at 3.4-3.5 MPG. Speed at this RPM is 31-36 MPH.

---

Boat:......1996 Outrage 21
Engine.....1998 Mercury 200 carb
Prop:......Vengance 14.5 x 17
Fuel:......50 Gallons
Water:.....5 Gallons
Air temp:..75 degrees
Water/wind:Calm
Calibrated FloScan and GPS data.

RPM.......GPH.....MPH......MPG
750......1.75.....3.2.....1.77
1000.....2.00.....5.1.....2.47
1200.....2.50.....5.9.....2.28
1400.....3.10.....6.6.....2.06
1600.....3.60.....7.1.....1.91
1800.....4.00.....7.5.....1.82
2000.....4.40.....7.6.....1.67
2400.....6.00.....8.3.....1.34
3200.....8.00....24.6.....2.98
3400.....8.25....27.5.....3.23
3600.....8.50....29.3.....3.34
4000.....9.00....32.5.....3.50
4200.....9.50....34.4.....3.51
4400....10.25....36.0.....3.40
4600....11.50....38.0.....3.20
4800....12.50....39.6.....3.07
5000....14.00....41.5.....2.87
5600....18.00....46.0.....2.47

posted 01-12-2008 09:44 PM ET (US)            

The two stroke engine is a gas dynamic engine, and best efficiency occurs when the least amount of intake charge goes out the exhaust. This is not merely an RPM issue but is an issue of RPM and load.

The hull has two kinds of drag: wave making (form) and frictional. Frictional goes up as the square of the speed, but is also dependent on the surface area in the water. Wave making decreases with the square of the speed above planing.

The net result of the drag is a U shaped curve with minimum drag somewhere above clean planing speed but increasing after that.

posted 01-12-2008 11:30 PM ET (US)            

Outboard: 10% of the HP per hour for gallons used. 4000 rpm optimum.
Carbed inboard: 10% of the HP per hour. 3000 rpm optimum.
EFI inboard: 8% of the HP per hour. 3200-3400 rpm optimum.
Diesel: 5% of the HP per hour. Best rpm 200 off max.

There is no magic with EFI, a carbed motor and EFI will have similar mixture and timing at optimum RPM. Any motor will have detonation problems if it is run lean or with too much timing. So maybe 10% better for EFI if it has a O2 sensor to control the mixture, the carb is probably jetted a little rich for extra insurance and maybe that’s why they are still running fine after 20 years like mine.

We know that at slow speed the carbed engine wastes most of its fuel out the exhaust so there is potential for big savings if you troll or go slow a lot.

My kids run my 90 Rude all summer while we are out cruising and I don’t seem to put any more gas in it than my buddies identical Montauk with a 90 ETEC.

I would love to have a shiny new motor but just can’t justify it until the old one goes boom.

posted 01-13-2008 09:44 AM ET (US)            

Dan from Tollyfamily has given some estimates above(gph), but I'm not certain that his estimates are for maximun efficiency or average use, or full throttle.
I assume his estimates are for all around average use.

I also have some estimates that have proven very close over time, although never measured with the accuracy of a Flo-scan.

I have always estimated that with 2-strokes, at maximum rpm was close to 10% of horsepower, and maximum efficiency was just about half at around 5%.
For example: When I had the 25 Revenge WT, w/250 OX66 EFI, best cruise effieciency was around 3800-4000 rpm, and used somewhere in the 12.5 - 13 gph. At 26 mph it averaged over 2 mpg. On days with little wind and chop, and long cruises, some though I was nuts claiming 2.5 mpg. But it seemed very accurate to the amount of fuel and miles covered.
I really never got a true estimate for full throttle, simply because I rarely did it for any length of time to find out. That's when a meter would have probably told me to SLOW DOWN.
To back this estimate up: http://www.yamaha-motor.com/assets/products/otb/bulletins/ bulletin_otb_2StrokePerf_OX666_250hp_017-COB-Z.pdf
Although not the same hull, the Cobia is a lighter, but wider, a ndlonger, and has a fixed top.
At 4000 rpm, the Cobia with the 250 OX66 is using 12.1 gph for an impressive 2.6 mpg.

The OX66 was super strong and never caused any problems, but if I were to re-power that hull, I would have leaned toward the Suzuki 250 or 300 with the larger prop and gear reduction. I think it would have been the most efficient available.
Although the max hp is 300. I wonder what the Yamaha 350 V8 would do on that hull?

posted 01-13-2008 10:51 AM ET (US)            

It is interesting that with all engine options on the smaller 205 and 235 Conquest boats the optimal mpg occurs at boat speeds between 19 and 26.8 mph, a pretty big range.

On the 255 Conquest the same is true till you get to twin 200 Verados. In that case there is a pretty flat band between 16 and 30 mph for optimal cruise.

posted 01-13-2008 12:04 PM ET (US)            

--the motor
--the boat

For two-stroke motors there tends to be a sweet-spot in the operating speed range where they produce power most efficiently. The 4,000-RPM range seems to be a common speed.

Once a boat gets on plane it ought to operate at a fairly constant efficiency, and one would expect that further speed increases will require more power in a more or less consistent fashion. However, I believe there is another trend occurring in the hull behavior as speed increases.

Generally in a planing boat as speed increases the wetted surface decreases. This should reduce drag. With the Boston Whaler classic v-hull, it seems like some configurations of engine and propeller can lift the hull farther out of the water while on plane than others. The more hull out of the water the less hull drag. So we see a trend where the HULL FACTOR may tend to increase with increasing speed.

posted 01-13-2008 04:06 PM ET (US)            

The 1985 1.8L Johnson 140 V4 (I suspect this motor was about 125 HP) that I recently removed from the 18 Outrage had to run between 4250 to 4500 to reach 30 MPH. Much too busy for my liking and probably past the optimal fuel efficiency point for that motor. In contrast, I can run the 2.6L 150 at 3700 RPM or so to get the 18 Outrage moving 30 MPH.

I had a fuel consumption curve for the Yamaha Ox66 225 that I had on the 22 Revenge which was confirmed by a friend's Yamaha Fuel Management gauge for his Ox66 225. It's been more than 4 years since I've had that boat so I'm not sure what I've done with the curve but distinctly remember that 4000 RPM was the inflection point on the curve for that motor where fuel consumption starting going up significantly per RPM. I recollect a little over 9 GPH at 3500 and about 11 GPH at 4000 RPM for that motor. Best fuel economy occured in the 3500 to 4000 RPM range which coincided with the 25 to 30 MPH "comfort zone". The Revenge had a top speed of 44 MPH at 5400 RPM.

The 27 Whaler WD with twin 225 Fichts has a Navman F3100 fuel flow gauge. I haven't recorded data at all the RPM points but can tell you absolutely that the best fuel economy (approximately 1.4 MPG) occurs at 29 MPH (4000 RPM). With that big MPG readout, you can't ignore the economy, its staring you in the face all the time. The cruising "comfort zone" for the 27 Whaler is about 27 MPH (3750 RPM) to 31 MPH (4250 RPM). Top speed is 45 MPH and the Navman indicates just slightly over 1 MPG at this speed (44 GPH).

So just by the "seat of the pants" feel, for my Whalers powered with 2-stroke V6s to reach the 45 MPH zone, the 4000 RPM point seemed to be the point where fuel economy and comfort started dropping off together. Thus, I rarely ran or run any of the motors above 4000 RPM and they all seemed to be quite at ease with that.

posted 01-19-2008 07:42 PM ET (US)            

The fuel efficiency is not tied only to the motor, but it is quite complex. If the new motor weighs more, its weight works against improved fuel economy. If the new motor is not fitted with the optimum propeller, it works against improved fuel economy. If the overall combination does not put the motor into its most optimum operating range, it works against improved fuel economy.

There is a general feeling that the brake specific fuel consumption of a motor is not constant, but, rather, the specific fuel consumption changes slightly as a function of the operating speed of the motor. It is widely recognized that specific fuel consumption tends to be best around 70-percent to 80-percent of full operating RPM. For example, Tom W Clark says his motor produces the best fuel economy at 4,200-RPM. If we can guess that his maximum engine speed is about 5,500-RPM, then 4,200-RPM is about 76-percent of full throttle, or right in the middle of the range suggested as being the optimum specific fuel consumption. It may also be that this engine speed gives a good boat speed and puts the propeller into spin at a rate where its efficiency tends to peak as well. And the hull may contribute to the improvement, too. Perhaps the hull generates enough lift at this speed to reduce the wetted surface, resulting in less drag.