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Author Topic:   Fuel economy: 2-stroke vs 4-stroke
jimh posted 08-25-2002 06:36 PM ET (US)   Profile for jimh   Send Email to jimh  
Here is some real world data which compares the performance of the same boat with a 2-stroke 90-HP engine and a 4-stroke 90-HP engine:

Mercury 90-HP 2-stroke
MPH = 25.5
GPH = 5.7
MPG = 4.5

Mercury 90-HP 4-stroke
MPH = 28.2
GPH = 6.3
MPG = 4.5

The same comparison again, this time at Wide Open Throttle (WOT):

Mercury 90-HP 2-stroke
MPH = 36.8
GPH = 12.0
MPG = 3.1

Mercury 90-HP 4-stroke
MPH = 36.4
GPH = 9.1
MPG = 4.0

(Source: This is a site that uses Frames [which are horrible] so I cannot get to the exact page with the data. You might get there with this Hyperlink )

jimh posted 08-25-2002 06:51 PM ET (US)     Profile for jimh  Send Email to jimh     
On this boat, the 4-stroke engine is a $2,000 up charge. For every hour we operate the boat at WOT we will save about three gallons of fuel. If fuel costs about $2/gallon, we save $6/hour at WOT.

This means that after about 333 hours of operation (at WOT) you will have saved enough on gas to have paid for the 4-stroke upgrade with the savings.

Of course, in 333 hours of WOT operation you will have travelled 12,133 miles. I don't know about you, but on a 500-mile 9-day cruise last summer we had about ten minutes of WOT operation. Most of the time we were at cruise speed. You recall that in the data above the fuel economy in MPG was the same at "cruise" throttle settings. (The 4-stroke had about a 10% speed advantage, however, so the comparison is not exact.)

jimh posted 08-25-2002 07:04 PM ET (US)     Profile for jimh  Send Email to jimh     
Let's assume you are a real speed merchant and you do operate the boat at WOT almost all the time. This raises the question: "Will the motor survive 333 hours of operation at WOT?"

My intuition tells me that most outboards will not survive this long. I cannot imagine an outboard lasting at WOT for 12,000 miles of operation.

My conclusion is that the 4-stroke engines have some advantages but do not expect to recoup your greater costs from fuel savings.

I know I have not factored in the cost of the 2-stroke oil, but this is somewhat offset by the lower maintenance costs. In 333 hours of operaton you would have had to change the crankcase oil many times in a 4-stroke. Lets say that we changed it six times (which is pretty conservative). This might cost you as much as $400 in parts and labor. At WALMART prices you can easily buy brand-name oil around $10/gallon, so that is 40-gallons of oil. Mixed 50:1 (worst case) that will handle 2000 gallons of gasoline.

In 333 hours of operation at 12 GPH you will burn about 4000 gallons of gasoline, so perhaps there is a few more dollars saved in the 4-stroke. You'll have to spend an extra $400 on the oil for the 2-stroke, over and above what you would have spent on the oil-changes on the 4-stroke.

However, consider the opportunity costs of having your $2,000 additional money tied up in the 4-stroke. It will take the average guy quite a while to get 333 hours of WOT operation in, and all that time the fellow who bought the 2-stroke has his money invested at 5% earnings. So each year he earns $100 additional income from his $2,000. Thus, if it takes you longer than four years to run up the 333 hours of time at WOT, you will be money ahead with the 2-stroke!

jimh posted 08-25-2002 07:14 PM ET (US)     Profile for jimh  Send Email to jimh     
The boat in this example is a TROPHY 1703 that weighs about 1800# with the base engine. It is comparable to the 170 Montauk.
jimh posted 08-25-2002 07:17 PM ET (US)     Profile for jimh  Send Email to jimh     
Now if the buyer of the boat had to finance the purchase, we should consider the extra interest charges on the 4-stroke package. It is easy to see that borrowing an extra $2,000 to buy the four-stroke engine will cause the time frame to increase before the fuel economy can repay the additional costs!

This gets more interesting all the time!

jimh posted 08-25-2002 07:26 PM ET (US)     Profile for jimh  Send Email to jimh     
Another point: in order to get to the break even point you'll have to run at least 333 hours at WOT, and this will mean you will have burned over 3,000 gallons of gasoline in the 4-stroke, which will have cost (conservatively) about $6,000.

So you cannot earn back your savings until you have spent at least $6,000 on gasoline, plus the $400 on oil changes, or about $6,400.

And you spent $2,000 more on the engine to begin with! This means you have about $8,400 invested, just getting to the break even point in the deal.

After many years and about $8,400 invested, you begin to save money. You won't earn any money, you will just avoid spending some. Your total cost of ownership will now be slightly better than the guy with the 2-stroke engine.

I know, I know, you cannot look at the boat and motor as an investment, but you can look its true costs!

Dick posted 08-25-2002 07:39 PM ET (US)     Profile for Dick  Send Email to Dick     
I don't know where you are coming up with your figures. I do my own oil changes on my 4 stroke and 3 quarts of oil and a filter costs about $20.00, all Mercury products. If I had a 2 stroke I sure wouldn't run Walmart oil in it. Compare apples to apples, Merc TWC3 is going to run $18.00 to $20.00 a gallon.

I also didn't buy the 4 stroke to save money on fuel consumption, although that is nice. I bought it because it runs smoother, idles better, trolls better and I don't have to put up with the stinky exhaust of a 2 stroke.

To me well worth the extra investment.

Try one you may like it.

jimh posted 08-25-2002 08:12 PM ET (US)     Profile for jimh  Send Email to jimh     
I was basing the oil change costs on about an hour of labor ($60) and parts ($15). Yes, you can save by doing it yourself, but you don't have that work with the 2-stroke, thus "apples to apples" as you say.

As for the oil, you can get WALMART brand for about $6/gallon. At $10/gallon you can often get the OEM labeled oil. Also, several users have reported excellent results with the WALMART oil, which by appearance looks exactly like the Quicksilver/Mercury product. That's where that cost figure comes from.

Your endorsement of the other virtues of the 4-stroke are legitimate, but I don't think there are any tangible costs or savings associated with them. How much is it worth an hour to not have a certain smell in the exhaust? That is hard to say; I actually like the smell of outboard motors as they remind me of boating!

As for trolling, it is unfortunate in this comparison that figures were not included for operation at slow speeds. Many people tend to think the 4-stroke will be automatically more economical at slow speeds, but this remains to be demonstrated by measurements.

One consideration that has not been included in this analysis is the environmental impact of releasing all the extra fuel into the water and air. At the moment the costs of that are not borne by the operator of the outboard. The extra pollution can be emitted without extra charge.

Dick posted 08-25-2002 09:19 PM ET (US)     Profile for Dick  Send Email to Dick     

I think I stated that I didn't buy the 4 stroke planing on saving enough money to cover the extra cost, or any money on operational costs.
Where do you get a $60.00 shop rate? We are at $99.00.

Who cares what it costs to run it if you enjoy it? If we were concerned about dollar to mile we would be riding bikes rather than enjoying our boats.

If you enjoy the stink of a classic 2 stroke, mixing your gas and oil or adding oil to an oil injection tank more power to you. Just don't knock progress.
The only advantage I know of for a 2 stroke is at idle they keep the mosquitos away.

Lagged posted 08-25-2002 09:23 PM ET (US)     Profile for Lagged  Send Email to Lagged     
Well, how much would it cost to get West Nile :)
David Jenkins posted 08-25-2002 10:54 PM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
Most boaters do not buy a 4-stroke because of the money they will save by doing so. Like people who buy Lexus automobiles, individuals who buy 4-strokes value quietness, smoothness, and reliabilty. They also are willing to pay more to avoid unnecessarily polluting the environment.
bocadrew posted 08-25-2002 11:00 PM ET (US)     Profile for bocadrew  Send Email to bocadrew     
I am curious to read other real world posts on this subject. It had seemed to me that those on this forum that switched to four stroke were very impressed with fuel consumption (perhaps that was from an old 2 stroke to new 4 stroke, and not a new 2 stroke to new 4 stroke.) Although I have never driven a four stroke the quiteness that others talk about sounds very appealing to me. Also as someone who keeps their boat in the water, I pay more than two dollars a gallon for gas at marinas not to mention the hassle of getting there.....drew
Dunk posted 08-26-2002 01:00 AM ET (US)     Profile for Dunk  Send Email to Dunk     
Real world.... My brother has my 72 16'7 with my 86 110hp Johnson. A friend of his has a 73 16'7 and just bought a 115 4 stroke Yam. They had them in the water last month together. Both loaded about the same 25 gals of fuel, them and couple kids each. From a dead start it was joke. The old 110 Johnson was up and out of the hole and down the bay by 150 yards before the Yam was even on plane. Top end wasn't fair because I had blueprinted the bottom on that Whaler before I traded it to my brother. It had 10-12mph on the same hp Yam 4 stroke at top end... On the same run to Cape May and back for fuel comsumption the 4s Yam won. It burned 10 gals and the old OMC swallowed 12.5gals.
David Jenkins posted 08-26-2002 08:28 AM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
Are you saying that it took the Yamaha 115 hp engine more than 10 seconds to get the boat on a plane?
whalerron posted 08-26-2002 08:41 AM ET (US)     Profile for whalerron  Send Email to whalerron     
jimh - You missed one very important point.

4 Stroke motors are not as environmentally friendly as most people believe.

Yes, 2 strokes burn oil and release burnt and some unburnt oil into the environment. So, some people say that a 4 stroke is more environmentally friendly. When the oil is changed in that 4 stroke, where do you think that oil goes? Although it is collected at recycling centers, only about 60% of used motor oil is currently recycled [1]. The rest is sold to businesses that use oil furnaces which burn used motor oil. This is because only "pure" used oil can be recycled. Oil that is contaminated with things such as solvents, gasoline, antifreeze or water cannot be recycled and it is extremely difficult to prevent contaminated oil from being poured into the collection tanks[2].

At some point, the bottle or container that was used to transport used motor oil must be thrown away. That bottle will end up in a landfill somewhere and it won't be the only oil contaminated bottle buried there.

The real reason that auto manufacturers have pushed the oil change intervals out to 6000 miles or more is not because the oil is any better and it's not because the oil doesn't get as dirty in 2002 cars as it did in 1972 cars when they were new. The real reason is because the government is trying to limit the amount of used motor oil that is burned and released into the air from "used motor oil" burning furnaces.

Most oil filters are not recycled [3]. Every oil filter contains a substantial amount of used motor oil and those filters are an environmental hazard.

One last thing to think about is the contaminants found in used motor oil contain: Lead, barium, zinc, cadmium, chromium, arsenic and benzene [2]. How many people get used oil on their hands when they change their oil? What is the cost of that exposure to the cancer causing contaminants found in the oil of that 4 stroke?

This discussion centers on the environmentally concerned 4 stroke owner who takes his used oil to a recycling center. I have not even begun to address the harm caused by some 4 stroke owners who dispose of their oil illegally [1][2]


jimh posted 08-26-2002 10:14 AM ET (US)     Profile for jimh  Send Email to jimh     
Another way to look at this situation:

Suppose there was not a easily distinguished technical difference between the motors. In the example above, one is a 2-stroke internal combustion engine and the other is a 4-stroke. Let's drop that out of consideration. Instead, assume that there is no difference between the fundamental technology of the engines, or at least we don't know what the technology contained in them really is.

Instead of referring to them as 2-stroke and 4-stroke, lets just call them the GREEN and RED engines, respectively.

Let's ignore the warm, fuzzy feeling that people get from owning a "low emission, environmentally friendly 4-stroke".

On the basis of the performance cited above, and the anecdotal report from dunk, are you still willing to pay $2,000 more for the GREEN motor than the RED motor?

Here are the attributes of each:

--Costs $2,000 more
--Is much more complex mechanically and electrically
--weighs more
--requires regular oil and filter changes and disposal
--uses slightly less fuel, but will take 12,000 miles of WOT to accumulate the fuel savings needed to repay the higher price
--produces lower noise levels at some operating speeds
--produces lower emissions

--costs $2,000 less
--very simple mechanically; less complex electrically
--weighs less
--no regular oil and filter changes and disposal required
--uses same fuel at cruise speeds, but uses slightly more at WOT
--produces more noise at idle speeds and mid-range speeds
--produces higher emissions

My feeling is that lacking the little glimpse into the technology of the engine that the words "2-stroke" and "4-stroke" convey, the real attributes of each engine can be presented for evaluation without prejudice.

Look over the attributes listed above an consider if you'd pay $2,000 more for the GREEN engine on that basis.

russellbailey posted 08-26-2002 10:44 AM ET (US)     Profile for russellbailey  Send Email to russellbailey     
whalerron makes some good points with references in his post regarding environmental impacts of used motor oil. I'd like to add more info to that. I'll state first that I clearly believe either a new-style 2-stroke or 4-stroke has significant environmental benefits over a 4-stroke.

1. Oil that is not recycled is classified as either specification (spec) oil or off-spec oil (40 CFR 279). Spec oil meets low levels for metals and halogens, and has a low maximum flash point (a measure of volatility). Only spec oil can be burned in most boilers/furnaces. Off-spec oil is burned in only Resource Conservation and Recovery Act (RCRA)-certified units, which must meet very stringent levels of control. A trivial amount of oil is burned in small home heaters without control. All told, the used oil that is burned is combusted very cleanly and recaptures a useful energy source.

2. By comparison, standard 2-strokes blow 1/3 of their oil directly into the air/water.

3. Oil containers will be generated by either new 2-stroke oil or new 4-stroke crankcase oil, and these can be recycled. Used oil is mainly collected in reusable containers.

4. Used 4-stroke oil clearly contains carcinogens that come from combustion products - I normally wear gloves changing our vehicle oils, but don't worry about incidental exposure. Compared to autos, the oil amount from boats seems low.

5. With a traditional 2-stroke, you are blowing about 33% of the oil/gas mixture directly out into the water and air. Gasoline contains numerous carcinogens, benzene among them.

Finally, regarding jimh's question about the GREEN or RED motor, I could no sooner buy a new RED motor than I would cut the catalytic converter off my car. I would not trash a perfectly functioning RED motor for a GREEN one, but I would definitely pay the extra for a GREEN one.

I for one am glad that by 2006, EPA mandates will require all new motors to be green.

SuburbanBoy posted 08-26-2002 10:49 AM ET (US)     Profile for SuburbanBoy  Send Email to SuburbanBoy     
It is good to see some staunch holdouts for 2-smokes. One consideration is that the 2-smoke pumps its excess gas and oil directly into the lake/sea water. This is without the benefit of any sort of containment device. Perhaps we should equip our 2-smokes with a catalytic converter, similar to those fitted to later Yamaha 350 2-smoke motorcycles. It allowed them to compete with the 4-strokes on exhaust emissions.


russellbailey posted 08-26-2002 10:55 AM ET (US)     Profile for russellbailey  Send Email to russellbailey     
With all the editing I do of other's work, you'd think I would have done a better job editing my own. I meant to say

"I'll state first that I clearly believe either a direct-injection 2-stroke or 4-stroke has significant environmental benefits over a traditional 2-stroke."

dgp posted 08-26-2002 11:22 AM ET (US)     Profile for dgp  Send Email to dgp     
Geez, jim, if I look at this boat/motor economic justification issue from a purely analytical standpoint I would never buy a boat. I'd just rent or charter one as needed.
Yes, I spent more money for Otto's little engine but mainly for the "drivability" or operational characteristics; easier starting, better low speed operation, less noise and lower smoke/smell conditions.
OutrageMan posted 08-26-2002 11:22 AM ET (US)     Profile for OutrageMan  Send Email to OutrageMan     
I have been doing a lot of research into alternative energy - solar, wind, etc. One constant is the question about "cost recovery."

I think that question is pointless.

In construction, do you ask that same question of the hardwood floors, or of the marble counter tops? No, it is just looked at as a cost.

There are many benefits of a 4 stroke engine. Just as there are certain drawbacks when compared to a 2 stroke. Rather than looking at from a cost recovery model, why not just make those pro/con arguments as you would any other decision.

This "cost recovery" discussion might be more relavant if the manufacturers of these engines were using it as a sales/marketing scheme.


Jimm posted 08-26-2002 11:29 AM ET (US)     Profile for Jimm    
From what I've read, The difference in noise is not that great at higher RPM's. I do not know this first hand so I may be wrong.
prj posted 08-26-2002 11:40 AM ET (US)     Profile for prj  Send Email to prj     
Well stated russell, as i believe this discussion will fall primarily down the lines of a person's typical political affiliations. Most of the following observations are generalizations and not to be taken personally. Most of the following generalizations are based upon personal experience with members or proponents of another political party:

"It is my opinion" shall be inserted in front of all following statements.

That republicans tend to measure costs and values of things/issues in terms of what either comes out of THEIR pockets or goes into THEIR pockets with little regard for big picture concepts and impact on others.

Discussions of taxes with Republicans primarily wind up being referenced with the phrase "my money".

Environmental degradation is a quanitifiable cost, albeit more difficult than simply counting what you pull out of your wallet.

That the Republicans currently in office with the Bush administration give not a measurable damn about the nation's environment in any way other than methods of exploitation. This opinion is very strongly bolstered if not proven by the FACT that the majority of the executive positions in the Dept. of the Interior (read NPS, BLM, public lands and the environment in general) are staffed by former and future advocates, attorneys and board members for exploitive industries including Mining, Timber and Oil. This as opposed to staffing the Dept. with say....Environmentalists? how about Scientists? Bill Moyers has done a couple of scathing condemnations recently on his PBS show.

How does this relate to 4-stroke v. 2-stroke? If told that the lone advantage of a 4 stroke would be reduced emissions at a higher dollar cost, i can guess which way an unfortunate number of Republican voters might purchase.

sorry for political discourse, but this topic was rife with issues that fall into the realm. Is "rife" a word? should that have been "ripe"?


fno posted 08-26-2002 12:00 PM ET (US)     Profile for fno  Send Email to fno     
One other point. Not applicable to those who don't trailer their boats, but I buy my fuel at the local B & B for $1.05 No mixing of fuel, no guessing the gallons, no smoke other than from everyone elses 2 strokes. It's a moot point anyway. 4 strokes and low emissin 2's are the way of the future after 2006.
bocadrew posted 08-26-2002 12:02 PM ET (US)     Profile for bocadrew  Send Email to bocadrew     
PRJ, that is crap. I am a republican because of freedom, not money. I believe in freedom, democrats dont.
bocadrew posted 08-26-2002 12:32 PM ET (US)     Profile for bocadrew  Send Email to bocadrew     
anyway back to 2 stroke vs 4 stroke.......
masbama posted 08-26-2002 12:41 PM ET (US)     Profile for masbama  Send Email to masbama     
Not many time you see Bill Moyers mentioned on a whaler forum! This will all be moot anyway because in 2006 we will all be buying big fat 4 strokes or complicated DFI 2 strokes. My rule: A motor put in salt water-buy simple. My suggestion: buy all the 2 stokes you can before they stop making them.
prj posted 08-26-2002 12:53 PM ET (US)     Profile for prj  Send Email to prj     
Not wholly true Outrageman, in construction we do look at recovery of cost issues, usually couched as maintenance/repair/longevity over the lifespan of a building or project.

patrick, a democrat who believes in freedom.

jimh posted 08-26-2002 01:20 PM ET (US)     Profile for jimh  Send Email to jimh     
It would facilitate the discussion of the fuel economy of 2-stroke and 4-stroke engines if we could please keep political party names out of the discussion. Thank you.

I began this thread with some real-world data, the first I have seen with a 90-HP engine, that showed what I thought was some surprising results, viz., that the fuel consumption at cruise speed was identical. I have heard many citations of improved fuel economy for the 4-stroke engines, but these results are not as encouraging as I would have thought.

Engine makers advertise clearly that the fuel economy can be better, citing numbers like 39% for example. But when you put the real costs with these numbers you see that fuel economy is not a real cost savings avenue.

Salmon Tub posted 08-26-2002 04:03 PM ET (US)     Profile for Salmon Tub  Send Email to Salmon Tub     
What makes a Honda 4 stroke outboard more environmentally superior to a 1968 Chevy Camaro? Both 4 stroke engines, both carburated. The Honda is superior to conventional carbed 2 strokes, but how does it compare in general - pollutants released to gallons of gas burned.
In automobiles, I beleive the evolutionary path was: control of exhaust (EGR, Catalitic Converter...) then control of intake (fuel injection). The main problem with 2 strokes is the fact that they discharge unburned fuel along with the exhaust. This was also a problem with cars. except for the 4 stroke outboards that are fuel injected, there is not much to compare to. We should maybe compare a Honda 115 to a Honda 4 cyl auto and see how they compare.
jimh posted 08-26-2002 05:11 PM ET (US)     Profile for jimh  Send Email to jimh     
As it happens, in the case cited by my example above, both the 90-HP engines are carburetor induction engines.

It may be that a comparison between a 90-HP carburetor induction 2-stroke engine and a 90-HP fuel injected 4-stroke engine would yield better fuel economy numbers for the 4-stroke AND fuel injected engine.

However, engine makers currently don't seem to advertise that their fuel-injection engines get better gas mileage than similar carburetor engines (at least in the case of Mercury). Although there is much anecdotal reporting of better fuel economy of EFI vs Carburetor, I would like to see more measured data.

jimh posted 08-26-2002 05:45 PM ET (US)     Profile for jimh  Send Email to jimh     
It might be interesting to consider the case to two 2-stroke engines, one conventional caburetor induction, and one sophisticated DFI-low emissions. Here is the data for these engines on a 19-foot TROPHY:

At CRUISE speeds
150 Mercury 2-stroke
MPH = 27.4
GPH = 11.2
MPG = 2.5

150 Mercury 2-stroke DFI Optimax
MPH = 25.3
GPH = 9.5
MPG = 2.7

At WOT Speeds

150 Mercury 2-stroke
MPH = 37.2
GPH = 19.3
MPG = 1.9

150 Mercury 2-stroke DFI Optimax
MPH = 36.4
GPH = 18.2
MPG = 2.0

Here the numbers look better, at least the "green" engine is getting better fuel economy at cruising speeds, but the story takes a turn for the worse when you look at costs. The up charge for the Optimax engine is $4,571.

If we apply the $2/gallon gas to this, we need to save 2285 gallons of gasoline to recoup our costs. The differential on GPH consumed is only 1.1, so this implies we will have to run at WOT for 2077 hours before the fuel economy has repaid our savings. Since we are now running at 36.4 MPH, we will have to travel about 75,600 miles before the fuel economy of the DFI engine had paid for itself.

Absent flat out racing, going 75,000 miles--three times around the world--is a lot of miles. It took me nine days to go about 500 miles last summer in a relaxed type of cruise, so that implies that it would take me 1350 days to travel 75,000 miles. Let's say was a maniac and went cruising 50 days a year (probably more than most). It will be twenty seven years before I get back to even on the costs.

Of course, the other guy who invested $4,571 for twentyseven years may have seen enough return to have a few bucks in the bank.

Wow, these numbers are worse than the 90-HP, don't you think?

Wreckdiver posted 08-26-2002 06:40 PM ET (US)     Profile for Wreckdiver  Send Email to Wreckdiver     
It seems to me that you have to consider the weight of the two engines as well. My boat was the only 2000 Montauk the local dealer ordered with a 2-stroke engine that year. As a diver, I wanted the lighter engine because the difference in weight was worth a set of doubles in the back of the boat. I have been told the extra weight didnít matter but we had three people and five tanks in the boat last weekend.
Salmon Tub posted 08-26-2002 06:41 PM ET (US)     Profile for Salmon Tub  Send Email to Salmon Tub     
What I find interesting is the apples to apples comparison that seems not to make sense. I would think that the Merc 150 either Opti or Carb would have the same gear ratio the same prop, and being that they seem to be tested on the same hull, give the same speed at cruise, how do they determine cruise speed, at an arbitrary RPM? Say 3000 or 3500? It may be that since the 2 stroke carb. is running a bit faster, it may have given a bit better mileage if they were run at the same speed. In 1 hour of cruising time, the Opti would be 2.1 mikes short of the boat with the carburated engine. At 2.7 MPG, it would need to burn another 2/3 of a gallon to catch up which would bring the performance even closer together.
Salmon Tub posted 08-26-2002 07:02 PM ET (US)     Profile for Salmon Tub  Send Email to Salmon Tub     
One other point, I have read claims by EPA type agencies that a 2 stroke will release up to 30% of the fuel unburned into the water. So then in the 1st post where Jim states the GPH consumption, this may account for the difference between 12 and 9 GPH, but why such a small difference between the Carb. and the Opti? Doesn't direct injection eliminate fuel from entering the combustion chamber before the exhaust port is closed? Does this mean that the Opti 150 requires a higher throttle position to reach the same RPM? How about this - If the carb. 150 burns 19 GPH at WOT, that is approx. 3 gallons an hour wasted, which is what the average car burns traveling at 75 MPH. If you took a three gallon container of gas and poked a hour in it large enough for a stream to pour out and empty the tank in 1 hour, it would be about a small trickle. This being the case, theoretically, the exhaust of an engine that is releaseing that much unburned fuel should also be combustible. I have not put a lighter behind my outboard while I wash it out, but I have not noticed a strong enough scent of gasoline to support this either. I think that a little bit of liberal mathematics was included in some of those calculations.

I think the application of 4 strokes does have it's place. This would be the best situation for guys who keep their boat on a lake, start to troll from the dock, or a few hundred yards away. Who troll all day long, and do little running. The reason I say this is because the one advantage that 4 strokes have is that they do not coke up (load up). They can run for hours at idle without any excessive fouling. The one thing that 2 strokes do not handle well is hours and hours of idleing.

jimh posted 08-26-2002 07:55 PM ET (US)     Profile for jimh  Send Email to jimh     
The precise conditions under which the data were obtained are not known. Inasmuch as the boat maker and the engine maker are both part of the Brunswick comglomerate, you would hope that the data has the bless of all three companies.

Yes the slight differences in speeds that are noted as "cruise" could be important to some. Generally the cruising speed of a vessel is that speed which gives the best range at a reasonable rate of advance. In other words, the crankcase speed the engine/boat/propeller conbination operates most efficiently.

You cannot make linear interpolations of the performance between the data points given and have any reliability of your results.

David Jenkins posted 08-26-2002 09:54 PM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
If you don't mind the loud noise or the smell, if adding oil to the gas is not a major inconvenience for you, and if you are not willing to pay a little more to help the environment and conserve natural resources, buy the 2-stroke. If, on the other hand, you like the idea of owning an engine that is so quiet and smooth at idle speed that you can't hear it running, you would prefer to not be able to smell the exhaust and you get satisfaction of spending a little more to emit fewer pollutants into the environment, buy the 4-stroke.

For me, the main issue is not which will cost me more or which will pollute less. What gets my attention is how quiet the 4-strokes are. And smooth. And reliable.

vdbgroup posted 08-26-2002 11:31 PM ET (US)     Profile for vdbgroup  Send Email to vdbgroup     
One day, we are all gonna meet our Maker!

I hope, of those last few days of being on this good earth, we are n't left with the lingering doubt of whether the four-stroke or the two-stroke was the right choice, but rather did we use what we had to the fullest enjoyment.

Fishcop posted 08-27-2002 01:11 AM ET (US)     Profile for Fishcop  Send Email to Fishcop     
37 posts later......
In our fleet of boats, we have two 21' SeaRay Laguna boats. Both are 1993 and have identical equipment. One has a 1993 200hp Merc. Offshore and the other has a 2001 200hp Merc. Opimax. During the same day and covering the same area at the same RPMs, the 1993 Merc Offshore burns 40gal and the Optimax burns 25gal.
A 20' RHI (rigid hull inflatable) that we have is equipped with a 130hp Honda 4stroke. The boat is lighter and as others have stated regarding 4strokes, is "very, very quiet". This aids in the stealth needed to do our job. The boat when taken on the same route as the SeaRay boats burns 22 gallons.
Now I do not pay for the fuel on these boats, but I am concerned with range and the ability to get from "A" to "B" in a hurry. The 4stroke Honda is (as the officers call it) is a "dog". The cost of the Honda was very expensive and does not make up for it in fuel savings.
I wish I had more comparisons for you, but the fishing is getting better and I am spending less time working.

James posted 08-27-2002 02:01 AM ET (US)     Profile for James  Send Email to James     
Sometimes the "real world" comes down to this:

1. I bought a boat to relax and have some fun with my family and friends.
2. Excessive loud noise leads to headaches and fatigue (Please see item 1).
3. Breathing engine exhaust gases makes the crew ill (Please see item 1).

I bought a 4-stroke Mercury because it is noticeably quieter than the Mercury 2-stroke that we also test trialed. The 2-stroke had noticeably higher exhaust gas emissions, especially after we experienced the four stroke. I also do not have to live with the continual oil/gasoline mixing mess.

Did I get along before, with a 2-stroke? Yes, absolutely! Do I want to continue to deal with the issues associated with a 2-stroke for a less than 10% savings in the purchase cost of a new boat. No!

These are issues of well-being whose true value is quantified differently by each of us. I frankly cannot see myself ever buying a 2-stroke again. Why? Please see item 1!


EddieS posted 08-27-2002 02:07 AM ET (US)     Profile for EddieS  Send Email to EddieS     
I am waiting for Yanmar to come up with a more powerful diesel outboard. They currently offer a 36hp as their largest in a line up of two motors. A 70hp Yanmar on the back of my 16' now that would be a real motor! Yanmar has been doing wonders with their larger motors in the HP/Weight ratios and I would not be surprised to see them come up with some larger outboards. The price is outrageous, but it would make an interesting comparison to the gas outboards in efficency.


hauptjm posted 08-27-2002 11:08 AM ET (US)     Profile for hauptjm    
jimh, going back to your example with the 150, your guy that banked the $4,571 would have $60,000 after 27 years if he got a 10% avg. return, $36,500 on 8% or $17,000 on 5%.

Of course, if we didn't spend the dollars we spend on our toys, we all be rich in dollars and poor in spirit.

jimh posted 08-27-2002 01:39 PM ET (US)     Profile for jimh  Send Email to jimh     
[Salmon Tub--your post was lost--sorry!]
jimh posted 08-27-2002 01:46 PM ET (US)     Profile for jimh  Send Email to jimh     
I am not really trying to conduct a debate about the virtues of 2-stroke vs 4-stroke. I just wanted to look closely at this real-world, measured data which allowed comparison of the fuel economy of engines of the same horsepower and used on the same boat.

I have heard many anecdotal reports of better fuel economy in favor of the 4-stroke. These hard numbers seem to take some of the edge off that notion.

In actual fact, if I were in the market for replacement motors, I would look very closely at the 4-stroke option.

Bigshot posted 08-27-2002 02:50 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
I have read many comparisons on 4 vs 2 stroke and Jim's is the closest in GPH which I believe to be because the "cruise" speed was in the upper 4k range. 4 strokes only shine from about 4.5k down to idle where I mainly drive. A 225 Johnson with carbs will burn about 13GPH at 4k(23.5 wot). The 225 4 stroke burns about 9, so does the DFI's. At WOT the DFI and the 4 stroke burn the same about 21+. So compared to a conventional, antiquated 2 stroke like my OceanRunner or say a 100GT Johnson, 4 strokes are gas misers. I would love to have a 4 stroke on my Hydra sport because 4gph at cruise is a big savings, but not worth $16k to upgrade......yet.

I will say for those of you who have never driven a 4 stroke for an extended period of time(weekend or more) you will not realize the benefits. This is my first 4 stroke I ever owned and trust me, I will NEVER buy a "new" 2 stroke again. I don't care how much more a 4 stroke costs, they are worth their weight in gold. My 70 Evinzuki is a 1999 and if someone offered me a 2003 Yamaha 2 stroke 90 even swap, I would pass on the deal.

mbking1 posted 08-27-2002 05:26 PM ET (US)     Profile for mbking1  Send Email to mbking1     
I have the Merc 60 4 stroke on my 99 Montauk. I love it! The Montauk has the 27 gallon tank. With moderate usage, you would not believe the range I have between fillups.The engine starts on first crank no matter how long between starts. I will never own another two stroke. Their is no comparison between the 4's Vs 2's. Mark
dgp posted 08-27-2002 05:32 PM ET (US)     Profile for dgp  Send Email to dgp     
mbk, is your's the EFI or carb version? How about posting some performance figures; speed @ rpm, fuel usage, etc? What prop / size are you running?
lhg posted 08-27-2002 06:29 PM ET (US)     Profile for lhg    
Hydra-Sport instead of an Outrage? What treason.
cyclops posted 08-27-2002 10:08 PM ET (US)     Profile for cyclops  Send Email to cyclops     
Hey MBKing1,

I would also like to hear about your setup and perfomance of the 4 stroke 60 on your montauk.

FISHNFF posted 08-27-2002 10:52 PM ET (US)     Profile for FISHNFF  Send Email to FISHNFF     
I know of those with new injected engines who get much much better fuel economy. But anyway, here are my personal findings. My boat is a 1998 Alert 17 with a tall, modified Montauk console. Most of my offshore trips with a 1996 Merc 75 2-stroke got about 4MPG. My newer 2000 Merc 90 4 sroke gets about 5+MPG. This is with 2 persons, 48-58 gallons of fuel, and (hopefully) 3 icechests (151,151,124) and a 35 gallon barrel with around 25 albacore and ice. My last trip done in pretty calm seas was 169nm on 33 gallons of fuel. Most of the trip was done at 25-28 knots with some 34 knot blasts. Straight line to the spot was 52 miles, but it took me closer to 70 due to little detours. My snail trail on the GPS was all over. Here's where autopilot would help.


Bigshot posted 08-28-2002 10:00 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Not really treason more like reason.

When I bought my 20' Hydra with a 225 , T-top, leaning post, washdown, baitwell, combing bolsters, etc. My bud bought a 17' outrage with a 150, bimini, and a skibar for the same price. I'll take the Hydra-Sports will he.

Now used.....nothing but a Whaler.

Salmon Tub posted 08-28-2002 11:59 AM ET (US)     Profile for Salmon Tub  Send Email to Salmon Tub     
Some other facts to chew on: I get 4.5-5 mpg with the 90hp, I got 3-4 mpg with the 40hp on the same boat - Montauk, moderate load. I now cruise at 2800 rpm, 20 mph, I used to cruise at 4000 rpm at 18 mph. For the most part, the Motorhomes with the big block v8's get better milage than ones with big 6's or small v8's. Why is it that mom can squeeze 300 miles out of a tank of gas while the kids seem to burn that same tank in 200 miles?
Salmon Tub posted 08-28-2002 03:55 PM ET (US)     Profile for Salmon Tub  Send Email to Salmon Tub     
EddieS, regarding the Yanmar Diesels, spoke to a distributor in Canada today who said as far as he understood, they are not EPA approved for use in the US. I can not confirm nor deny that. He says that the 27hp diesel equals the output of a 45hp gasoline engine so I would imagine that the 36hp would be approximately like a 60hp gas.
jimh posted 08-28-2002 04:59 PM ET (US)     Profile for jimh  Send Email to jimh     
Re: the comparison of 4-stroke to luxury cars like a Lexus.

This comparison might apply, but not in terms of performance. Generally, at the same rated horsepower, people see better performance from the 2-stroke.

If a Lexus had worse acceleration than a Ford Pinto, it would not be selling as well. Well, perhaps that is extreme.
But in general, the upscale car comes with upscale engine performance. When you step up to a Lincoln from a Crown Vic, they keep most of the mechanicals the same, but they put new heads on the V-8, go to dual overhead cams, and tweak about 70-HP more out of the same block.

In the outboard motor case, the upscale (price) engine comes with the same or worse performance.

David Jenkins posted 08-28-2002 11:30 PM ET (US)     Profile for David Jenkins  Send Email to David Jenkins     
I am willing to concede that you may have to increase the horsepower for a re-powered Whaler to feel like a Lexus. This is what tobasco did when he bought his new 170 (he increased horsepower from 90 to 115). However, with a top-end speed of 50 mph, I doubt that he feels like he is driving a Ford Pinto.
JimU posted 08-29-2002 03:37 PM ET (US)     Profile for JimU  Send Email to JimU     
Much like the rest on this thread, I apparently don't have enough to occupy my time. But for the brave among us, some might like to put the four stroke cost recovery question into a discounted present value model. Bsed upon my recent experience, which I hope to change in the near future, I have a two year-old 90 2-stroke with 75 hours On the clock and a year old 40 2-stroke with 7 hours on the clock. At this rate, I may never pay for the difference. That's why I bought the two strokes.
Bigshot posted 08-29-2002 05:05 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Hell at that rate you may never break them in:)
EddieS posted 08-30-2002 02:08 AM ET (US)     Profile for EddieS  Send Email to EddieS     
Salmon Tub,

I think you may be correct about EPA approval on the Yanmar outboards. I could find very little information on the web but I notice that the Yanmar USA site does not even list them.

I was just reading some information on them and apparently they ran twins from SanFrancisco to Hawaii on 385 gallons of diesel! That is 2250 miles non stop.


dgp posted 08-30-2002 08:24 AM ET (US)     Profile for dgp  Send Email to dgp     
The Yanmar distributor in Louisiana will sell you a brand new 27HP Yanmar diesel outboard for around $12,000. Still want one?
The 36HP model is not available in the US but you can get them in Mexico or Canada.
Lewis posted 08-30-2002 10:47 AM ET (US)     Profile for Lewis  Send Email to Lewis     
I just types a long post, typed my password in wrong, was instructed to use back button to try again and my post was gone. To say the least...........frustrating as hell.
rb posted 08-30-2002 04:34 PM ET (US)     Profile for rb  Send Email to rb     
Ironic how easily we justify spending more for a Whaler hull over a conventional hull while we condem the cost of a 4-stroke over a 2-stroke.
peteinsf posted 08-31-2002 02:18 PM ET (US)     Profile for peteinsf    
Salmon Tub, how does 27hp diesel = 45hp gas work? Fatter Horses? Never heard this one. If it true my 6hp yanmar aux. sailboat should pull away from those honda models.
Sal DiMercurio posted 08-31-2002 08:10 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
You guys are way off base, thinking or believing the 4 stroke gets better fuel economy, or puts out less emissions.
The Evinrude FICHT gets twice the fuel economy, & puts out much less emissions.
I own a 2000 - 200 hp FICHT, on a 1980 - 20' Outrage.
I cruise at 3,500 rpms, between 30 & 34 mph.
My boat is rated for only 175 hp, my cruise milage, is "OVER" 5 mpg, troll fuel cunsumption at 2.4 kts is 3/10 of a gallon per hour.
Bass & Walleye boats did a comparison on the 225 yam, 225 honda & the 225 Evinrude, all on the same typa hulls, the Evinrude litterally ate the 4 strokes alive, as far as power & speed, blew them both out on fuel economy, by no less then 3 mpg over the competition.
Emissions were a joke, as far as the 4 strokes go, they put out "FAR" more then the Evinrude FICHT 2 stroke.
Plus the 4 strokes weighed 138 lbs more then the 2 stroke.
A friend of mine just bought a Yam 225, put it on a 23 Scout, we both fished the same area for 2 days, leaving & returning at the same time, both put 102 & 107 miles respectivly on our engines, ran together in & out, trolled the same amount of time.
We both pulled in to fill up, I took 18 gallons, for over 5+ mpg, he [ 4 stroke yam ] took 52 gallons.......duh!
Now, can any of you guys please tell me the advantage of owning a 4 stroke, & don't give me, it's more quite, because i talk on my cell phone running 3,500 rpms without yelling, &A i can hear you fart at troll.
Just for the record, my Outrage runs 60.3 mph on the radar, with a 14.25 x 21 Stiletto prop.
marlee809 posted 09-01-2002 10:17 AM ET (US)     Profile for marlee809  Send Email to marlee809     
I would be interested to have decible readings at idle slow troll and mid range speed and top speed. I have exp. on a 25 Sea Ark with twin Honda 130's at idle/slow speeds it great at high speeds it is close.
It would be nice to have some official readings.
FISHNFF posted 09-02-2002 12:40 AM ET (US)     Profile for FISHNFF  Send Email to FISHNFF     
Last trip was 130 total nm, about 50 running each way@4200-5000RPM, 30 trolling @2300RPM, for 25 gallons.
1998 Alert 17 with tall modified Montauk console, Merc 90 4S, 42 gallons fuel, 2 batteries, 128 and 151 icechests loaded with Albacore and ice, and a 35 gallon barrel 1/2 full water.


Peter posted 09-02-2002 12:19 PM ET (US)     Profile for Peter  Send Email to Peter     
This is quite an interesting topic and since we have had a mostly rained out weekend and I had a little time here I thought I'd do a little estimating of the payback period for my 1986 22 Revenge WT if it were repowered with a Yamaha F225 instead of the Yamaha 225 Ox66 EFI that it currently has hanging on its transom. It's my belief that Yamaha was asking for a $4,000 premium for the F225 (the 225 EFI is now out of production).

Since there is no real world published data for a 1986 22 Revenge with either motor, I decided to search for substantially equivalent data. Fortunately, Pursuit published a near apples-to-apples comparision (225 EFI test weight was lighter) for its 2470 Walkaround (WA) model and the performance figures for that model with the Yamaha 225 EFI are remarkably close to the performance figures I have experienced with my Revenge 22/225 EFI over two years (100+ hours) of use. So I am assuming here that an F225 on a Revenge 22 WT would perform similar to the data published for the reported 2470 WA/F225 combination.

According to Pursuit, the 2470 WA (no bottom paint) with the 225 EFI has the following performance:
1500 7.9 2.5 3.14 353
2000 9.1 4.9 1.85 208
3000 20.3 7.3 2.78 313
4000 31.5 10.3 3.05 344
5000 40.4 16.3 2.48 279
5500 45.1 24.2 1.86 210

Pursuit reports that the 2470 WA (no bottom paint) with the F225 has the following performance:

600 3.0 0.8 3.75 422
1000 5.0 1.2 4.13 464
1500 6.6 1.9 3.45 388
2000 8.2 2.7 3.02 340
2500 9.4 3.8 2.46 277
3000 14.5 5.1 2.84 320
3500 21.1 6.5 3.24 364
4000 27.2 8.3 3.27 368
4500 31.5 10.4 3.02 340
5000 35.3 13.5 2.61 294
5500 39.3 17.6 2.23 251
5800 40.7 19.6 2.07 233

Conditions around here usually allow comfortable cruising in the Revenge between 3500 and 4000 RPM which yields real average speed over ground, as measured by GPS, of about 26 and 31.5 MPH respectively. Since Pursuit publishes data for the EFI at 4000 RPM and not at 3500 RPM, I'll use the upper cruise speed of 31.5 mph at 4000 rpm as the first point of comparison. At this RPM/speed combination, Pursuit reports that the EFI burns 10.3 GPH (based on my experience, I think it is more like 11 GPH). To obtain this same cruising speed, the F225 must operate at 4500 RPM and according to the report it burns 10.4 GPH. Thus, using Pursuit data, at the same cruising speed, the 4-stroke yields [b]no[b/] fuel savings, no additional range and no payback period. Using my data, at 11 GPH and gas at $2.00 per gallon, payback (assume no investment of savings) requires 3,333 hours of operation at 4500 rpm (~105,000 miles traveled). For my 75 hour seasonal usage, that would take approximately 44 years to achieve. At the more typical 50 hour/season usage, payback is 66 years. Also, in either of the hypothetical 44 or 66 year payback periods, the F225 with all of its extra moving parts will have revolved 100 million more times than its EFI counterpart to go the same distance!

What about the savings at operating at wide open throttle (WOT)? Well that comparison is somewhat difficult because the F225 doesn't achieve the same top speed as the 225 EFI. For comparison, I picked the top speed of the F225. According to Pursuit, the F225 is capable of pushing the 2470 WA to 40.7 at 5800 RPM and burns 19.6 GPH. According to Pursuit, the 225 EFI obtains 40.4 MPH (close enough) at 5000 RPM and burns 16.3 GPH (my data suggests the burn rate at 5000 RPM and same 40.5 MPH speed is more like 19.0 GPH). Thus, according to the Pursuit data, the 4-stroke burns 3.3 GPH more to go approximately 40.5 MPH, therefore there is no payback period derived from fuel savings. If you use my data for burn rate, there is also no fuel savings from the 4-stroke at 40.5 MPH and no payback period derived from fuel savings. Not only is there no payback but, for every hour of operation at this speed, the F225 turns an additional 48,000 revolutions. If the frictional wear is the same for both, the F225 will clearly not last as long and there is a greater penalty for operating the F225 at WOT.

What about a comparision at a trolling speed of 5 MPH? According to Pursuit, the F225 burns 1.2 GPH at 1000 RPM. My data suggests that 225 EFI burns about 2.0 GPH at 1000 RPM to go 5 MPH (Pursuit didn't publish data at this level for the 225 EFI). At a 5 MPH (typical "No Wake Speed") the payback period is approximately 2,500 hours (50 years at 50 hours/year, 33 years at 75 hours/year).

At the price premium Yamaha had been asking, I never thought that the purported fuel savings from an F225 made sense, economically, to justify choosing it over the less complicated 225 EFI for me. From this comparison, now I know that is the case. Perhaps this is one of the several reasons why the 4-stroke never really caught on too well until the environmental regulations were applied to the outboard motor industry.

Well if there is no real finacial gain to be had and there is a transom static weight disadvantage then what are the other reasons to go with the F225 over the 225 EFI for a hypothetical 22 Revenge WT repower? Quiet operation, no smoke, better for the environment?

Well is the environment really getting a benefit? One purported benefit from the 4-stroke is that less hydrocarbons are being emitted during operation. Thus, of the approximate 10 or 11 GPH used by each motor at cruise, the 225 EFI should emit more hydrocarbon waste. However, there must be a greater environmental toll during the manufacturing process for the F225 over the 225 EFI due to its additional moving parts plus disposal once the F225 is spent. When you take that into account does the purported benefit of the F225 outweigh the greater environmental toll it takes to make one? The environmental comparision really should be done on a cradle to grave basis. I think the jury is still out on this one.

Although some rave about the no oil smoke from a 4-stroke, oil smoke is not much of an issue for me. I'll be happy to give that up the day that the big diesel rigs give up the black soot. I'm sure that the volume of black soot emitted in a year from the trucking industry far exceeds the volume of 2-stroke oil smoke from outboard motors.

As far a quiet operation, I actually like to hear my motor while it is operating. It tells me quite a bit about what's going on back there without actually to look at the tachometer. Also, from what I've read, at WOT the sound level differences are not that great.

Well after all of this, I conclude that I'm not yet a 4-stroke convert.

Ed Z posted 09-02-2002 11:56 PM ET (US)     Profile for Ed Z  Send Email to Ed Z     

Isn't great that there are so many different advantages to each and every type motor out there... This way everyone can choose the advantages most important to them and select a motor that satisfies their desires... I personally have been a 4 stroke since 1972 (55 hp Bearcat) and currently have been very happy with my 85 hp Bearcat... The reason mostly is that I can troll fish very slow all day long at 1.2 MPH with very quiet and vibration free enjoyment... But that's only the advantages I'm interested in and may not be important to the next guy...
Bigshot posted 09-03-2002 10:26 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Funny how these topics are biased towards whatever the owner/poster has on his/her transom.

I read the "Boating" write-up on the 23 scout with a 225 opti, 225 ficht, 225 Yamaha 4s, Mercury 225 4s, and Honda 225. The ficht was the fastest and got about the same MPG that the 4s did but also cost the same. The optimax was the biggest guzzler and also the cheapest. The Honda and Yamaha and Mercury 225 4 strokes all came in close with the Merc having the price advantage but unfortunately not available yet so WTH?

I own a 225 Johnson and at 4000 rpms on a 20' Hydra-sports I am running about 33 and burning about 13gph. I think there is a big difference between 13 and 9 or 10 like I said above. Plus at 1000 rpms a 4s or DFI will burn less than 1gph where mine burns over 2....major difference when trolling for 6 hours, gives me almost an extra hour of cruise time on the way home. Crucial with a 85 gallon tank. My Hydra runs 53 on a good day so who cares if the 4s will only do 49 or 50. As far as a 20' with a 200 doing me the GPS. Comparing a DFI to a a 4 stroke is comparing red apples to yellow apples. Where the 4 strokes shine is the dependability compared to far. Price is the same, weight is close, etc. Comparing a 4s to my 1994 Johnson is apples to oranges.

Comparisons are great but to those who avg 150 hours per season, payoff time is much quicker, plus my 4stroke will idle all day long with no plug fouling and the only thing you hear is the pisser hitting the water. People are amazed at how this engine runs. My 90 yamaha burned almost 50% more than my 70 4stroke does at cruise with about the same performance sans holeshot.

Salmon Tub posted 09-03-2002 04:16 PM ET (US)     Profile for Salmon Tub  Send Email to Salmon Tub     
Peteinsf, I assume that what you have is a sailboat with a relatively large (as compared to the honda outboard) diesel inboard engine. Assuming that you found an identical boat as yours but with a transom mount outboard that was rated the same HP as your diesel consider the following. I have no idea as to what your prop size is, nor max rpm, but I would imagine that the prop is most likely bigger in diameter than on the Honda. Your pitch is probably higher too, but you most likely have have different gearing and a lower top RPM. Your diesel accelerates slower too. What I mean is that while an outboard will reach max RPM's quicker than the diesel, both boats will experience prop slipage until the hulls get enough momentum underway. Once this is the case, yes, your diesel may not be able to overtake the outboard in a calm channel, but, continue out into open water, especially where there are swells. Your bigger prop will result in less deceleration while climbing waves than the smaller prop on the outboard. Put that same prop onto the outboard, and you will see it lugging and losing speed on each wave. A diesel has the torque to turn a bigger prop with less gear reduction at a lower RPM. So, realistically, the more important factor is prop size x gear ratio x max 'acheivable' rpm rather than stated horsepower. That is why they always rate HP at a rate of RPM, say 90 hp at 5500 rpm. If I take my prop off and launch the boat how much real HP am I producing at 5500 rpm? This is also why switching say from a 15" pitch to a 17" pitch (an increase of 13.333%) does not mean your top end will increase by 13.333%, which would mean that you would go from say 38 mph to 43 mph. This is because your WOT rpm's would come down due to more resistance from the bigger prop. This is why all those stick boats we see out trolling around have big displacement diesels with relatively low HP ratings, they don't have a high top speed, but they also can plow through large waves without being slowed down and pull decent sized nets or gear. The props on those Yanmar 36 outboards looks about the same as most 60 hp gas outboards. As is, HP, as a system of rating, is not great when it comes to Marine application.
lhg posted 09-03-2002 06:13 PM ET (US)     Profile for lhg    
So, am I reading all of this correctly? The 4-strokes do not offer an extended life, nor do they save very much in fuel, except at idle speeds? And their real environmental benefit is only noticable during start-up and idleing around, and while trolling?

A few days ago, 20 miles offshore on a smooth Lake Michigan, I observed an ore carrier steaming along, and leaving a 20 mile long trail of yellowish sulfur laden smoke from it's stack in the atmosphere. It would take thousands of 2-stroke outboards idleing along to leave a pollution trail this large. But then again, nobody said life was fair. The outboard engine business & and it's customers were a simple target, while the big polluters, jet aircraft, marine diesel pleasure craft, diesel trucking, railroads and shipping, go unchallenged.

homey posted 09-03-2002 07:42 PM ET (US)     Profile for homey  Send Email to homey     
It certainly is interesting reading. This comparison, 2stroke vs 4stroke. It really boils down to whats important to the consumer.
I recently purchased a 1991 outrage cuddy/whalerdrive. The boat has twin 1989 Johnsons 150hp. I'm personnally not crazy about them and found out my starboard motor will not last much longer.
Rather than do a rebuild I'm considering on repower. For me, technology, quiet running, less smoke, slightly better fuel mileage, and reliability are more important than blistering speed and acceleration. I like to be able to cruise along nicely and still be able to have a conversation...I've been on plenty of 2 stroke powered boats and 4 stroke powered boats(all speeds)and for me there is no comparison. I prefer a Japanese made 4 stroke. Just my 2 cents.
Salmon Tub posted 09-03-2002 09:22 PM ET (US)     Profile for Salmon Tub  Send Email to Salmon Tub     
In reality, the whole pollution debacle probably started one day when a Senator's or Congressman's wife was at a launch ramp and got smoked by some really poorly tuned outboard. She probably asked why the engine was smoking like that and was told that it is normal. Then she probably decided that hubby should pass a bill banning them. Isn't it funny how these kind of things get started, and don't forget to take your prop off when you wash down, or else she might just be there when you throw the engine into gear and stick your hand in there. Then she might just ask hubby to ban propellers.
Peter posted 09-04-2002 08:29 AM ET (US)     Profile for Peter  Send Email to Peter     
It is pretty well established that the operating environmental benefit of a 4-stroke is not just at idle but at all operational speeds. Assuming the data from Pursuit is reasonably accurate, what I find very interesting in the high power 2 versus 4-stroke comparison that I did is how much energy the valve train and other components of the 4-stroke must consume to overcome the higher overall friction from the additional moving parts to thereby obtain the operating environmental benefit.

I believe I have read somewhere (perhaps here) that a 2-stroke passes approximately one-third of the fuel charge out the exhaust port in an unburnt state. If that is so, then in the F225 to 225 EFI comparision which suggested that they use fuel at the same GPH rate to go the same speed, the one-third amount that is discharged unburnt by the 225 EFI must be substantially burned in the F225 to drive the valve train. The data seems to show quite convincingly that it is not providing propelling thrust.

This leads me to think that if the DFI 2-stroke reliability improves, it could become the preferable "high power" repower plant for several reasons on a purely objective basis. First, the DFI 2-stroke might be more fuel efficient than a comparable high power 4-stroke since it has fewer or lesser massive moving parts. Second, in theory, and perhaps actually, it should have operating environmental benefits similar to a 4-stroke because the DFI is intended to prevent, or at least significantly limit, the discharge of unburnt fuel by injecting fuel after the exhaust port is covered. Third, it does not suffer from the lack of low end torque which becomes important when trying to maintain a plane in rough seas. Fourth, the initial capital investment seems to be lower. Finally, because it weighs less, it doesn't upset the static trim of a boat as much its 4-stroke counterpart.

Only time will tell which technology is the winner, if any, but I must agree with Ed Z's prior comment; isn't it nice to be in a country where you have to make such difficult choices?

Bigshot posted 09-04-2002 10:41 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
They have been working on orbital technology for over a decade. Orbital corp(or something) originated in Australia. They invented an airplane type engine with around 12 opposing cylinders in a circle. It was supposed to be the "wave of the future" in automobiles, etc. I believe the company went bust and Mercury bought their injection design from them and decided on making their own version. OMC was already working on their Ficht(which is believed to be a better design) from what I read. Basically Merc & Yamaha just increase fuel pressure to atomize the gas better along with a few other doodads. This is a great idea and will work great once the technology improves. Some believe Bombardier has already done so.

As far as weight, the 4 strokes and DFI weigh pretty close. 4 strokes have more moving parts but reley less on technology and fuel management. Without both, a DFI is just a 2 stroke. Will 4s get lighter.....maybe. Have 2 strokes shaved weight.....nope. A 115 in 1974 weighed 280+lbs, now it is 375. My 1972 25hp weighed 82lbs, now they are almost double. A 235 in 78 was 385lbs which is 10lbs heavier than a 75hp ficht and 30lbs lighter than a Suzuki 115 4s. I imagine boats will be built to handle the extra weight. But then again most boats back then were designed to handle twins which together weigh about the same as a modern single.

Who will money is on a tie between DFI and 4strokes. I think 4strokes are here to stay, unlike in the past. The need and desire is there to make sales. DFI will be right next to them as long as they can get their crap together and make a dependable alternative. I know I would not buy a DFI unless it was 135hp or less, even then I trust a 4stroke more, but I desire the DFI's performance. As far as price goes....about the same for both. For now my pick is 4 strokes but I think DFI will be a contender, thanks to Bombardier and Yamaha. Mercury needs to attend top their issues(read this months Boat US).

Peter posted 09-04-2002 11:32 AM ET (US)     Profile for Peter  Send Email to Peter     
Totally agree that 4-strokes are here to stay. Emissions regulations and their desirable attributes will ensure that. But for the high power range pushing the 23+ foot boats, I still think that 2 stroke DFI technology may ultimately dominate if the reliability issues relating to fuel management are substantially overcome. With the launch of the new 225 and 250 HPDIs, Yamaha, a fairly conservative player in my opinion, doesn't seem to think that it can put all of its eggs in the 4-stroke basket.
lhg posted 09-04-2002 01:33 PM ET (US)     Profile for lhg    
Mercury's new supercharged 4-strokes could change all of this, if they are reliable.
Peter posted 09-04-2002 01:51 PM ET (US)     Profile for Peter  Send Email to Peter     
I'm not convinced that a supercharged 4-stroke will do it. Will the supercharger get the power to weight ratio up to where the 2-strokes are while maintaining reliability and affordability? It seems that to keep the weight where it currently is, without a seachange of materials, they would likely have to abandon the big engine blocks, otherwise the weight might balloon to 700lbs or so. Also, where do you put the supercharger without making the cowling extra large? Starts making the I/Os look like an attactive alternative (win/win for for Brunswick).

I'm not in favor of making the engine hanging on my transom and exposed to salt air and water for nearly six months out of the year any more complicated than it has to be. The beauty of the conventional 2-stroke was its simplicity and reliability. I'm still of the camp that thinks that "there is no real replacement for displacement" and that will ultimately win out.

Bigshot posted 09-04-2002 02:07 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Problem is that they keep making displacement bigger for better reliability. the old v6's were 2 litre blocks, now they are over 3 litres. I agree on the simplicity but since I have to embrace technology, I want the good stuff like EFI, etc. What you are gonna see with these newer engines are more and more rebuilds. Back in the late 80's it cost $1500-2000 to rebuild a 90hp OMC and a NEW 88SPL could be had for around $3400. Today a 90 costs $6k and it still costs $1500-2000 rebuild. Now that a 225 4s costs $17k, you will see people replacing the powerheads for $5k before they replace the engine.
dnoha posted 09-04-2002 05:15 PM ET (US)     Profile for dnoha  Send Email to dnoha     
Lotís of interest and passion surrounding this one!

For the record, I have a 2 stroke 3cyl 40hp Merc. I didnít pick it out, it came bundled on the nicely priced 13í Super Sport I bought a few months ago. I like it very much, but then I donít know any better. As I said when I joined this forum, Iím new to power boating.

But something about this thread interests me anyway. You were attempting to focus on the fuel economy issues related to the 2 vs 4 stroke debate. Worthwhile. But in the ensuing debate, several people have talked about the improvements in both designs that should come over time. And itís that time thing that makes me think something else will change the equation.

Burning a fuel to release the chemical energy stored in it is something weíve pretty well mastered. Thereís probably not a lot of tweaking remaining to that energy extraction method. Like and marvel at them though I do, internal combustion (or combustion period, internal or external) engines are a woefully ineffective way of efficiently using the chemical energy stored in the fuels they burn.

The fuel cell methods of energy extraction are advancing rapidly and are inherently much more efficient and non-polluting. I suspect the 2 vs 4 debate will die in a few years once the price/performance of fuel cell powered electric outboards becomes competitive. And at the rate things are going, in the meantime the DNA engineers will create an aquatic critter that loves to eat the stuff that comes from our outboard exhausts.

Sal DiMercurio posted 09-04-2002 05:52 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
The 90 degree FICHTS,[ 200 hp & up ] were always reliable.
They did "NOT" have the problems of the 60 degree [ 150 & 175s ] engines.
The big [ 200 hp & up ] only had to replace the injector clamps, with bigger ones & thats the extent of their problems.
As i mentioned before, the 200 FICHT is giving me 5+ mpg, no other engine, including all the 4 strokes can even come anywhere near that.
Emissions,....... the FICHT beats them all by alot.
Bass & Walleye magazine put it very well, when they said, the FICHT is the blue print & future of the outboards, the Optimax is the gas guzzler of the whole lot.
lhg posted 09-04-2002 06:33 PM ET (US)     Profile for lhg    
I have observed just the opposite of the above post. The pre-2002 big block Fichts, 200-250, had tons of problems, and the smaller ones were fairly decent, but any 2001 can be suspect, and almost all of the 2000 and earlier were nightmares. Even Bombardier has said they were all made from poorly engineered and produced parts.

Optimax a gas guzzler? Hardly. Don't believe everything you read here. None of the Evinrude Fichts even have the 3 star pollution rating of the Opti 135.

Sal DiMercurio posted 09-04-2002 10:14 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
I'm sorry, but your misinformed.
There were no problems with the big engines, the 150 & 175s were the problem enguines.
As far as emissions, up until last year, the Evinrude FICHT was the only 2 stroke engine allowed on Lake Tahoe, it surpassed the 2006 EPA requirements & the 4 strokes.
Merc just met the requirements.
Seems you info is from way back as far as Evinrude engines.
Bombardier would not warranty the smaller [ 175s and lower hp ]OMC engines, that were built from 2000 or before, those were problem engines, they warrantied the 2000 - 200s & up right from the time they bought OMC, because they were not problem prone.
Merc still puts out more emissions then the Evinrude.
Evinrude is the lowest emission outboard made today, including the 4 strokes.
whalerjake posted 09-04-2002 10:48 PM ET (US)     Profile for whalerjake  Send Email to whalerjake     
I love this site. We are all sold on Whalers, so we debate the motor choice.

This is healthy stuff for all.

Here is my two cents... I went 4-stroke because I slow troll a lot. I spend one hour wide open and 3 hours slow trolling live bait and Rapalas.

I'll never win a boat race though. 50hp Honda on a 17.

I guess it's just different strokes for different folks. :)

Bigshot posted 09-05-2002 10:24 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
I'm with Larry. I heard the big block Opti's and Ficht are the problem engines. I have also seen about a dozen 200+ engines for parts where I have seen NO 175 and smaller. My friend has (2) 2000 or 2001 ficht 225's and they gave him many headaches. One finally blew. I have heard nothing but praise on the v4's.
Peter posted 09-05-2002 11:32 AM ET (US)     Profile for Peter  Send Email to Peter     
My town had two 1999 or 2000 200hp FICHTS on its 27' Whaler Vigilant police boat. The starboard one caught on fire in 2000. According to the Police captain, they were nothing but trouble for the entire time they had them. (I suspect too much idling did them in). They were replaced this year with Merc 200 EFIs.
DaveH posted 09-05-2002 02:02 PM ET (US)     Profile for DaveH  Send Email to DaveH     
Fuel for the fire:

JD Powers and Yamaha report better reliability with high horsepower 4s than 2s.

Bigshot posted 09-05-2002 04:52 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Kick ass!(as Cartman would say)

Owners of new boats with four-stroke electronic fuel injection (EFI) outboard engines report the fewest number of engine problems, while owners of boats with two-stroke carburated outboard engines report the most problems, according to the study.

Boaters who purchased a new boat equipped with a two-stroke outboard engine report twice as many problems as those who purchased a boat equipped with a four-stroke outboard engine, resulting in a general conclusion that for both two- and four-stroke engines, the larger the engine is, the fewer problems are reported, said the release.

"Among the five technologies used in outboard engines, the quality level of four-stroke EFI and carburated engines is unparalleled," said Eric Sorensen, director of the marine practice at J.D. Power and Associates, in the report. "In additional to quality, four-stroke engines are cleaner and quieter than two-stroke engines and are very fuel efficient. The fact that they weigh and cost more, and donĻt accelerate as rapidly as two-strokes is not much of a deterrent for many boat owners."

tomol posted 09-05-2002 06:50 PM ET (US)     Profile for tomol  Send Email to tomol     
Jeez, I leave for a couple of weeks and miss a post with 86 responses. I confess my eyes glazed over after reading about half of them, but here is some real world info.

I replaced my 90 Yamaha 2-stroke with a 100 Yamaha 4-stroke two years ago. Here are the numbers:

The 4-stroke was $400 more than the 2-stroke, although from what I read above that is no longer the case. I typically have one other person in my Montauk with dive gear, 23 gallons of gas (+10 for the run to San Clemente Island), two batteries and two HUGE hoagie sandwiches.

I've been able to measure time/distance because I typically make long runs of 30 to 50 miles to dive spots where I anchor for the day and return. I navigate off the GPS so I know I keep pretty close to the rhumb line.

Cruise @ 3500 rpm 18 knots
WOT at 5200 rpm 32 knots
mileage @ 3500 rpm 3.5 mpg

Cruise @ 3500 rpm 20.5 knots
WOT at 5200 rpm 37 knots
mileage @ 3500 rpm 4.5 mpg

I don't know my mileage at WOT. I've never run it long enough at that speed to tell. Besides, 37 knots in that boat is a little frightening..


Bigshot posted 09-06-2002 10:43 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
I was just reading an article on the new Carolina Skiff with a F225 Yammie. They claim 7gph at 4000rpms. My 225 Johnson burns about 13 at 4k.
Peter posted 09-06-2002 11:12 AM ET (US)     Profile for Peter  Send Email to Peter     
Pursuit publishes 8.3 GPH at 4000 pushing the 2470 Walkaround so that sounds about right. But I don't think its a fair to compare the fuel consumption of the 2-stroke to 4-stroke based on the same RPMS, it has to be based on the same speed on the same boat where they are both doing the same amount of work.
Sal DiMercurio posted 09-07-2002 03:56 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Pretty obvious on Nates reply, different props.
5 mph difference at wot, same rpms.
I really do question these 8+ mpg on the 4 stroke, especially on a 24' boat.
How is it, my buddy gets 2 mpg with his 225 hp Yam 4 stroke, on a 23; fairly light boat.
I really must say, I feel someone is printing, their wishful thinking.
Between Bass Walleye Boats & my own tests, the best the 4 stroke gets, is 3.8 mpg, adding 5 mpg to that, seems really out of line, big time.
I'm sorry, I just don't believe it.
jimh posted 09-07-2002 05:08 PM ET (US)     Profile for jimh  Send Email to jimh     
Having just spent $18,000 for a 4-stroke engine can affect one's ability to properly measure gasoline consumption is the conclusion I have reached.
Sal DiMercurio posted 09-08-2002 09:07 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Jim, you hit the nail on the head.
FISHNFF posted 09-09-2002 12:36 AM ET (US)     Profile for FISHNFF  Send Email to FISHNFF     
Yes my newer 4 stroke gets better mileage than my previous 2 stroke. Yes it is quieter. Yes I do not miss 2 stroke oil (my 75 Merc had a chronic oil tank leak). I know I had to shell out some $$$$ to upgrade, and it will take some time to recoup the money spent. But that is not the only reason. When running long distances offshore, like 50+ miles, I just don't have the room to carry all the fuel, and ice chests, and equipment. Eliminating even one fuel tank or using a smaller one is a big help.
Get a bigger boat you say? I just love running the 17 way out there and seeing all those big boats ;)


ps. I also have a Grady 226 Seafarer

Bigshot posted 09-09-2002 11:13 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Uh Sal.....that is 8.3 GPH which stands for Gallons per hour, not MPG or Miles per gallon. Burning 8.3 on that pursuit is about 3-3.5MPG. The same carbed 225 would burn about 12gph which would be about 2.5-2.8mpg. I have a 1994 Johnson 225 and at 4000rpms and 30-32mph it burns about 12gph. Saving 4gph at cruise is major, especially with a 85 gallon tank. My 24 Baja with a 400hp BBC gets 3.3mpg at 35mph. So do not discredit a 4 strokes efficiency.

Like I said above, until you own one, do not think we are talking with our Johnson's here.

David Ratusnik posted 09-09-2002 05:16 PM ET (US)     Profile for David Ratusnik  Send Email to David Ratusnik     
Some 2 stroke smoke,,,, some savings in gas ( I run the cheapest 87 available),,, less rattle and shake,,, you've got to have more money then brains to buy a 4 stroke until your 2 stroke becomes anchor quality. .03 David
Sal DiMercurio posted 09-09-2002 05:29 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Bigshot, now you make sense.
2.5 - 3.3 is horrible mpg.
How is it, these companies can say they get x mpg, when they don't even get 1/2 that much.
Can someone please, tell me the advantage of buying a 200 or 225 hp 4 stroke over a 200 or 225 - 2 stroke Ficht engine?
The FICHT gets over "TWICE"" the "MPG" as the 4 stroke, weighs 136 lbs less, absolutly no smoke, less emissions, & costs less.
Please explain,........if you dare to try.
David Ratusnik posted 09-09-2002 07:24 PM ET (US)     Profile for David Ratusnik  Send Email to David Ratusnik     
Sal- Bottomline, you've got to put a ****load of gas thru a 4 stroke until the differential between it and the 2 stroke on your boat makes $$$'s sense. .03 (fact) David
David Ratusnik posted 09-09-2002 07:26 PM ET (US)     Profile for David Ratusnik  Send Email to David Ratusnik     
2 stroke
Sal DiMercurio posted 09-09-2002 09:28 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Dave, On 100 gallons of fuel, through my engine, I can run 500 miles & still have fuel left over, put the same amount in a 4 stroke, same hp, & your out of fuel in 300 miles at best.
Right from day one, the 4 stroke is behind & theres just no way it can catch up, not getting 1/2 the milage of the FICHT.
It's really sad, because many of these people who bought, or are going to buy, big hp 4 strokes, really believe their going to get better milage then a 2 stroke,'s simply not true.
Again, my buddy who bought the 23 Scout, & put a 225 yammi 4 stroke on it, is actually happy he's getting 2 mpg, because he dosen't know any better, he thinks all 200 hp+ outboard engines get 2 mpg.............thats sad.
jimh posted 09-09-2002 10:14 PM ET (US)     Profile for jimh  Send Email to jimh     
I have to temper what you are saying with the recent posting of fuel consumption numbers from the Evinrude website.

Evinrude themselves are saying that the 4-stroke Yamaha and Honda get better fuel economy than their Ficht engines. I know you are enthusiastic about your motor, but even its maker is not quite that positive about its relative fuel economy.

Sal DiMercurio posted 09-09-2002 11:36 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Jim, they say, 1/3 better, but everyone I know is saying 5+ mpg if run reasonable, like under 4,000 rpms.
I know i'm an exception, because i'm 50 hp over maximum rating, [ 175 ], mine is putting out, 222hp at the prop,so my engine never really has to work at all.
I can cruise at 40 mph all day long, & not run over 4,000 rpms.
My boat is a 1980 - 20' Outrage [ really only 19'10" ], weighs in at hull only, 1,600 lbs.
My engine is up on the 3rd hole, & the Stiletto hangs on through everything.
Even Bass & Walleye Boats magazine, says 5+ mpg, so I don't know whats with the company that builds them.
Bigshot posted 09-10-2002 10:23 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Sal....Ficht is designed to compete with 4 stroke consumption. In some operating ranges you can do better than a 4 stroke but for the most part 4 strokes are king. Your bud better be doing better than 2mpg in a 23' unless he is running WOT. No matter what you are running on, if you are running 4000rpms you are burning x amount of gas. The difference comes in MPG due to how fast you are going. For instance if you run 4000 in a 20' boat you will burn 8gph. If I run 4000 on a 30' boat I will burn about 8gph. The difference is you are running 38mph and I am running 22.

Ficht & optis are great engines, if you get one that runs. They get equivelent MPG to a 4 stroke with better performance due to torque curve and less weight. Ficht are not that much lighter than 4 strokes....about 50lbs lighter than a Yamaha. 100lbs lighter than a honda. Ficht technology will be supreme or equal to 4 strokes but the technology is not proven yet. Although the big 4 strokes are not proven yet, they have had no reliability issues like ficht and opti had when they came out. I think 4 strokes will be very reliable, but not as fast as a ficht.

You can talk all you want about price....a ficht costs just as much as a 4 stroke. reason why they are selling them at discounts is because most are scared to death to buy one. 4 strokes sell at msrp or close because people want them.....DFI they want but are affraid so a discount makes the sale. A 225 ficht lists for the same as a 4 stroke.

This argument was debated on the benefits of an optimax vs a carbed or EFI Merc 5 years ago. It will take X-amount of years to break even, etc. If that was the case then why pay double over a Bayliner. Does the same thing, goes the same places. How can we justify paying so much like David says....Well you guys are forgetting resale. My Montauk will sell for much more with my Zuki than it would with a 70 2 stroke. If you shop, you can get them for equivelent prices or close. Most people don't shop so therefore can not justify the price. We do not own Whalers because we are cheap bastards....if so we would be on the Carolina Skiff forum. This conversation is getting old.....real old.

russellbailey posted 09-10-2002 11:29 AM ET (US)     Profile for russellbailey  Send Email to russellbailey     
Quoting bigshot "No matter what you are running on, if you are running 4000rpms you are burning x amount of gas. "

This is only right if the engines have the same efficiency (i.e., gas consumption per hp). A DFI 2-stroke should be able to get somewhat higher efficiency than a 4-stroke - even auto makers look at DFI 2-strokes for research sometimes. Clark Roberts bore this out with his 135 Opti/115 4-stroke comparison on his 21 Revenge.

David Ratusnik posted 09-10-2002 01:18 PM ET (US)     Profile for David Ratusnik  Send Email to David Ratusnik     
"resale", what resale?? Run the 2 stroke until it becomes anchor quality. That way you keep your money as long as possible. Who knows in the interim you may change diversions and never have to buy that overpriced 4 stroke. For 99% of us a boat is not like a car, -- we can do without it. Like to spend money, electively buy a 4 stroke, hey resell and buy a new one every few years. Choices, choices, choices. .03 David
Peter posted 09-10-2002 01:29 PM ET (US)     Profile for Peter  Send Email to Peter     
It seems pretty clear from the Evinrude data (if you believe it is reliable since it is published from a significantly biased source) that the FICHT fuel economy was better at trolling speed and at high speed. In the cruising range it was slightly worse.

I'm not convinced that it is true that "no matter what you are running on, if you are running 4000rpms you are burning x amount of gas" (alternatively stated hypothesis: a given motor consumes the same amount of fuel at the same RPM regardless of what size boat it is pushing). If I have understood the hypothesis correctly, then the Pursuit and Carolina Skiff data, as well as the numerous Yamaha performance reports, do not seem to support it. Also, if it were true, then there would be no reason for Yamaha to publish the numerous performance reports for the various boat/engine combinations.

Wouldn't it be possible that to achieve 4000 RPMS in the heavier Pursuit you have to have a somewhat more advanced throttle position which would cause the engine to consume more fuel (i.e. 8.3 GPH vs. 7 GPH)? I am assuming that the differences are real and not related to some variations in the measurements techniques, data rounding, etc.) I admittedly don't know enough about engines to answer that question.

Once again, I say you cannot reasonably compare the fuel consumption of a simple 2-stroke (carb'd) to the other more advanced 2-strokes (EFI or DFI) or to a 4-stroke at the same RPMs. It doesn't mean anything. The data I've looked at clearly shows that they all have different power curves and that the 4-stroke seems to develop the same comparative power at higher RPMs across its entire operating range. You must compare fuel consumption of the competing technology at the same boat speed on the same boat in the same testing conditions where all test subjects are doing the same work.

Bigshot posted 09-10-2002 02:10 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
That is the most accurate way to do it Peter. But....if you prop a boat to run said redline of 6000rpms. If you are running 6000 and I am running 6000 then we are burning the same amount. Same is true for running 4000(for the most part). But what differs is the MPG which will change dramatically. Why do you think my Baja gets 3.3mpg? Because I cruise at 35mph. Now if that engine was on a 24 SeaRay, he might only get 2.2mpg but burn the same fuel at cruise.

David....If you really want to run until it is dead and get every bit of life out of it, then I would DEFINEATELY buy the most efficient engine on the market. Usually it takes about 700-1000 hours to make up the cost difference, so if you plan on running that or more...why spend it on gas. Plus engines keep getting more expensive and so does gas, so in 500 hours you will break even if gas jumps to $3 gallon from $2.

This is not a winning conversation here. Buy what you want, drive what you want. Keep repairing that 35 year old bearcat for all I care. I can say that I ACTUALLY went from a 2 stroke to a 4 stroke and have MUCHO positive benefits. You can read all you want and procrastinate and improvise and what ever else you feel the need to do don't have hands on experience. When you will see the light like so many of the 41% of merc products being sold are now seeing.

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