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Relatively new poster here, been floating around so far trying to learn as much as I can, and I have to say it is getting pretty confusing. Looking into my first boat. I have been asking around, and doing as much reading as possible, but have yet to get a straight answer. Some people recommend 4s and some 2s. The people that say go for the 2s say there is more torque in the midrange. The people that say 4 explain that while that may be true, the torque is only used at the beginning to get up on plane, and while at this point a 2 might be better, the 4 would be fine. They also say that because the 4 has more moving parts it takes more power just to run, and that 2s are more reliable. I have yet to see any dynos that would show the torque curve or hp curve, don't even know if they exist. I guess my question is, what is the real story with these motors? Is there a real world difference when it comes to how this difference in midrange torque affects the ride of certain boats? I assume that the answer will probably depend on the type of boat (size) in question, so let’s assume it is on a 20-22 ft center console type.
I rarely touch my throttles on my 30 proline with twin 225 hp 4 strokes. If a four stroke or a two stroke were turning 4000 rpm and in turn swinging my props, how would I know the difference? As far as having a wide power range (which is what the torque people really mean when they talk torque), it would be of some value if I were pulling water skiers but I'm not. It would be extra great if I had a two stroke in my car where a wide power range comes in handy so you don't need to shift so much but I think I'll keep my car with the four stroke and live with it.
Hyefly,
I have a 115/4stroke on a 20 feet or 6 meter 1750lbs walkie (hull only) it tops at 43 L.Miles and has instand planning with the 4 blade ss trophy prop.I don't think so, but maybe a 100hp 2 stroke does the same.
But dispite what is said I know it uses
less gas than my 70hp 2stroke and the gas overhere is 5.60 dollar a gallon and it doesn't stink when I troll because it doesn't use oil.
This is based on 3 test drives only with the 115/4 but I think it's pretty accurate because we developed a nose for gas and I topped it of all tree times(thats a little bit more accurate)
and yes when you are used to a 100 hp/2 it make sence to put on a 115/4 but I also think you gain a little power with the 115/4
I hate to admit it, but I didn't like 4 stokes in the begining. I think for me it was mostly just being around 2 strokes (and of course change is bad, right?) Anyway when I see the 4 strokes at the ramp powering on the trailer I'm amazed at how quiet they are. I will definately consider the 4 when I go to repower. The cost difference will be the major factor for me.
Just my .02.
I'm not familliar with the power curve difference of the fourstrokes v. two stroke. I have read the the 2's have better midrange, which is kind of confusing. In other appllications ie. motorcycles, the fours have better low and mid, and the two's have better top end.
Having owned two strokers for many years I went to a 4 stroke Yamaha about two years ago. I see very little difference in the torque curves. Atleast nothing that you feel in the boat operation. I really like the lack of oil smoke and odor. Noise level is such that wind noise is more of a problem that engine noise. This I really like. As for economy of gasoline, no comparison.. The 4-stroke cost MUCH less to operate. Glad I made the switch. In no way would I want to go back to a 2-stroke.
I currently have a 115HP 4s Mercury (Yamaha powerhead) and I love it. The EFI means instant starting even after weeks on the trailer. The fuel economy is fantastic.
Having said all that, if I had to buy another engine, I would look seriously at the new DFI 2s. They have all of the benefits I listed about 4s but weigh less. The soon to go in production, Envinrude E-TEC DFI impresses me the most. Many fewer parts than the Yamaha or Mercury DFIs or any 4 strokes. Fewer parts, less chance for things to break.
The bad news is both 4s EFI and 2s DFI cost a lot more than 2s carbs, but they do run better and pollute less.
I repowered with twin 4 stroke Johnson’s and the only time I see a diff is when I first jump on plane. Just a little slower than the 2 cycle. And when I am at the dock idling there is no noise from the engines or smoke. But I think each motor you asked about has it purpose and you have to make that decision your self. But for mileage and ease of operation you can’t beat the 4 strokes there main purpose for most is for crusing and to give you a smooth midrange operation. plus the gas savings I for one have cut my gas bill to a little more than half. and the motor are paying for them selfs a lot faster than I figured!! each time I go off shore the mileage is about 185 miles (64 mile out and trolling all day and back in.)and I have only been burning about 80 to 90 gal per trip the last trip we only burned 74 gal. before we would burn 150 gal or more!!!
Torque comparisons between 2s and 4s is WAY down at the bottom of my list for chosing a motor. Did I say WAY, it is WAYWAYWAYWAY down there. I'd say worrying about torque is more hype than useful for decision making. Changing props will make big changes if hole shots are an issue, no matter what the stroke. I own both 2s and 4s and in the politically incorrect minority with a 2s preference.
If torque is the reason fo rselecting 2 stroke over a 4 then there shouldn't be an issue. You WILL NOT relize the difference. If you think you will, get a 2 stroke and do like all the others that see and DONT hear my four stroke, just sahke your head. Also when you are "trying " to fill oil resevior and not make a mess, think of the four stroke. When you start you motor and the smoke rolls in your eyes , think of the four stroke. But al lest you WILL know when the moter is running.
For my use I prefer 2s. I run small boats and generally use 12 gallons or less per day. 12 gallons takes me at least 40 miles which is a pretty good daily run/ fishing trip. At $2.00 gal. I spend 24 per day. I could theoretically run a 4s, save a third, and only spend 16 per day, saving 8. If the cost difference between 2s and 4s is 1500, it would take 187 days on the water to make up in gas savings the initial outlay. I don't go often enough to justify the difference. By the time I got an additional 187 days in, the 4s would be out of warranty, it has a lot more parts to break and replace, etc. Then I'm spending money on 4s maintenance that I would not have to spend on 2s. (at least theoretically). For my usage, I don't see me ever breaking even. Give me a good ole carbed 2s, lighter, less things to malfunction, etc.
You gotta consider DI 2-strokes vs carbed 2-strokes vs 4-strokes. I have owned all 3, and I would never have a carbed 2 stroke again. But, the differences in the DI 2-stroke and 4 stroke are not much....same fuel use, 4 stroke is a tad quieter only at idle, both are more quiet at speed, throttle response a bit better in 2 stroke, you have to add oil to the 2 stroke but you also avoid oil and filter changes, which are messy if you keep the boat in the water. Neither make any smoke or sheen on the water.
Not sure I understand the question, but here goes.
Just recently I owned a 2 str 90 Yamaha and now I own a 4str 115 Yamaha. If what I am getting out of your question is how do they compare smaller 2 verses larger 4. It is like comparing apples to orangatangs different engine different sizes, different wieghts.
In my application the 90hp was on the extreme top end of power for the boat it was on and now the 115 is on the mid to low end of power for the boat it is on. Both have done remarkable jobs and I had no problem with the 2 str and have not had a problem with the 4.
I have read on this forum where some folks have said 2 str hp is more power, 4 str hp is not as strong. Balogna!!!! Hogwash!!!! Hp is Hp plain and simple.
4str power is more expensive, but quiet, no smoke, no oil to mix, little more maint. 2str power is cheaper, noisy, smokes and smells. Reliability well that is always the best till whatever you buy breaks the first time.
Thanks for all the help so far. There is no question that hp is hp, but its the torque that is different. I think most of the answers were right on line with what I am asking; how does the midrange torque difference effect the ride of the same boat, when comparing like hp motors. For example Yamaha 150 2sk and Yamaha 4 stk 150. I'm starting to get the feeling that there is very little difference.
The dfi 2 strokes get better fuel economy than 4 strokes not almost as good better.They are aprox 125 LBS lighter on a 200 hp size engine .On a twin engine setup thats 250 lbs on the back of a boat enough to seriously effect the attitude of a boat.The 4 strokes are weak in the mid range torque department which is a very bad thing .When you are running your boat in rough water and need to just keep it on plane thats where the torque comes in. You will curse that 4 stroke every time it falls of plane and you have to run faster than you want to keep it on plane .The 4s dont idle any better than the dfis just a little quieter .I know these things because I have owned both types.If you check with boat manufactures you will not find many that will recomend 4 strokes on their boats .Now a dealer will tell you what he thinks you want to hear.Horse power is not all it takes to do a job it take torque as well.Compare 2 300 hp truck engines one a diesel the other gas the diesel is able to tow aprox 6000 pounds more than the gas engine because of the difference in torque.4 strokes have thier place but dont let some boat test where they run 1/2 tank of fuel and 2 people fool you. Several companys have been guilty of fudgeing a little on the weight and speed of the 4 strokes. Just watch closely on the forum when you see these people trying to find the right prop for their 4 stroke its proably not the prop thats the problem but simply the lack of torque .
I repowered this year from a 250 carbed yammi to a 2002 250 Rude DI. The reason I went with a 2 stroke was gas mileage. I looked at various 4 strokes and they all weighed a 100 lbs or so more than a 2 stroke. As we all know added weight effects gas mileage and handling I did not want ot be hauling around an extra 100 lbs. forever. I have a bracket on a 25 foot boat, that 2 1/2 feet extension would have increase the effect of a heavy motor on the transome and the handling of the boat (changing the center of gravity).
A 2 stroke gives you a power stroke every second stroke, a 4 stroke every 4th stroke.
Actual performance-my old carbed yammi-I used 30-40 gallons of gas for a fishing trip (about 25 to 35 miles and used 35-40 gal of gas. With the new Rude for the same fishing trip I use 24 gal. optimum is 4000 rpms = 26 mph and 2.8 gph according to the fuel computer. I could not believe it, I have made the trip several times and it is pretty much the same. Oil useage is amazing.
Everyone is saying the 4 strokes are the future, but what about the Etec? I have read research where companies are trying to harness the Wankel (rotary) engine for outboard use.
Maybe I have added more questions here but I have given you my actual results on my boat.
Hope it helps.
For 43 lbs I will take the 225 4-stroke all day long. The 200 is a different story 108lbs can be significant depending on the boat. The 4-stroke 150 is actually lighter than the HPDI, this is likely since it is Yamahas newest design and they learned how to trim the fat. If this is in fact due to new designs it will find its way into the 200 and 225 4-stroke in the next model year or two.
As far as fuel consumption goes, the Popular Mechanics article cited above shows that the 4-strokes were better than the DFI to the tune of 2 GPH. In reality I believe the consumption between the two is essentially the same. However, once the 4-strokes move from throttle body fuel injection to direct injection they will likely be considerably more economical than the 2 stroke DFI.
I am somewhat familiar with the operational characteristics of both 2 and 4 stroke engines. In my opinion a 2 stroke will never run as cleanly as a 4 stroke due to the fact that a much larger volume oil is burnt per cycle in a 2 stroke than a 4 stroke. For this reason there will always be more emissions from a 2 stroke unless they find some way to improve the combustion characteristics of the 2 stroke oil.
Every test I have ever seen has a 4 stroke being significantly quieter than a 2 stroke at idles. Moderately quieter at mid range and slightly quieter at WOT. Personal experience supports these conclusions.
I would be betting on turbo and supercharged 4 strokes for the future of outboard motors; I just don't see how they are going to clean the 2 strokes up enough.
4 Stroke v. 2 Stroke, midrange torque and ride... 
and I topped it of all tree times(thats a little bit more accurate) 
