2 stroke or 4 stroke?

[rebelson]

can anyone tell me the advantages and disadvantages from 2 stroke to 4 stroke?

 

[mthieme]

Re: 2 stroke or 4 stroke?

2 stroke -
higher power to weight ratio - twice the potential of a 4 stroke
simpler construction - no valvetrain - which means they are lighter and cheaper
less fuel efficient
have to mix expensive oil
more emissions
noisier
days are numbered

 

[BillP]

Re: 2 stroke or 4 stroke?

2 stroke -
higher power to weight ratio - twice the potential of a 4 stroke
simpler construction - no valvetrain - which means they are lighter and cheaper
less fuel efficient
have to mix expensive oil
more emissions
noisier
days are numbered

Evidently you aren't aware of Etec's specs?

 

[kenmyfam]

Re: 2 stroke or 4 stroke?

I second Bill's post.

 

[steelespike]

Re: 2 stroke or 4 stroke?

The modern 2 stroke will perform better through a boader rpm range with less fiddling than a 4 stroke.Fuel use really is pretty much a wash except 4 stroke does better in certain very specific uses.4 stroke is generally quieter generally heavier more complicated with more frequent and complicated service intervals.Etec now has a 25 and 30 hp at 146 lbs for manual start.
177 lb electric start,power tilt and trim.
Additional 130 hp V4,65hp twin,55 hp multi fuel twin,and a bunch of HO motors.

 

[mthieme]

Re: 2 stroke or 4 stroke?

My apologies tothe Evinrude crowd.
I forgot a disclaimer.
You are right, I am unaware of the Etec specs.
I was unaware it is lighter and louder than a 2 stroke.

 

[tashasdaddy]

Re: 2 stroke or 4 stroke?

4 strokes, oil changes, valve adjustment, just more parts to wear or break.

 

[Silvertip]

Re: 2 stroke or 4 stroke?

Fuel economy comparisons between 2- and 4-strokes are very controversial. If you compare fuel economy at the same RPM the four stroke will win the arguement. What is missing from that comparison is speed. A two stroke will almost always be pushing the boat at a higher speed than the four stroke. So just be certain you understand the numbers before making a purchase decision. As for noise levels -- a four stroke at slow to medium speed is a tad bit quieter but at wide open throttle those dB numbers get quite close. The "observation" is that the four stroke is quieter but the dB ratings don't show that. A four stroke makes a different sound at wide open throttle so it only appears to be quieter. These are generalities so do your research to determine the degree of difference. As for durability -- four strokes have only been around in significant numbers for a 10 - 15 years. Two strokes have proven their worth over 60 - 70 years and many of those motors are still around, never been wrenched on except for tune-up and general maintenance. Only time will tell how well four strokes hold up.

 

[steelespike]

Re: 2 stroke or 4 stroke?

Here's a thought; lets take an average car given average service.Driven 150,000 highway miles.About 2,500 hrs.Driven on average at less than 1/3 to 1/4 of its rated rpm It will most likely need major work at least in the upper end in that time.not to mention timing belts/chains etc.Lower end still probably serviceable.
A typical outboard is probably driven on average at least at 2/3 its rated rpm and its like going up hill. I think the four stroke is in for more major service than the 2 stroke. 2 stroke only has the lower end to worry about.
Imagine how the hours add up on any marine engine driven mostly at its max rpm.

 

[Joe_the_boatman]

Re: 2 stroke or 4 stroke?

OK, I'll bite.

Ditto all the above. Also, the major 4-stroke outboard manufacturers (Honda, Suzuki, Yamaha) all have been building high output, light 4-stroke engines for many years (think motorcycles - CBR, GSXR, R1, respectively). In fact, Honda's B115 uses the Accord's block.

Basically, 4-strokes are quieter, heavier, and have lots more moving parts (timing belts, valvetrains, lubrication systems), but are more efficient (generally).

The new direct injection (DI) 2-strokes are a new breed of engine developed specifically to meet new EPA regulations (2006), and the market's desire for fuel efficiency. The DI manufacturers will tell you they're lighter, more efficient, and more reliable than 4-strokes. But, the technology is still in its infancy, and has yet to be proven as a reliable alternative.

If it's my money being spent, I'd put the DI's at the same price point as the 4-strokes. For a given horsepower and age, I'd get the less expensive one.

This may also help:
http://www.popularmechanics.com/outdoors/boating/1276841.html

See page 3 for fuel consumption data.

Last but not least, be prepared for fiery arguments for both sides from passionate owners defending the engine they just spent $10K on.....

 

[mthieme]

Re: 2 stroke or 4 stroke?

Fuel injection is in it's infancy ????

 

[jevery]

Re: 2 stroke or 4 stroke?

On the issue of noise levels, BRP publishes no E-TEC noise level numbers, and they?re fairly difficult to obtain. Wonder why? Get some Boattest.com test reports, drop the noise numbers in an Excel table, chart the table, and you?ll find out why BRP doesn?t publish this data

http://i539.photobucket.com/albums/ff354/21weber42/E-TEC/Noise75.jpg
http://i539.photobucket.com/albums/ff354/21weber42/E-TEC/Noise225.jpg
http://i539.photobucket.com/albums/ff354/21weber42/E-TEC/Noise250.jpg

I am able to produce either direct links or images of test reports to back these charts.

Sidenote - Trailerboats reports an earsplitting 110 dBA for the new 250 HO at WOT
http://www.trailerboats.com/output.cfm?id=1590697&sectionid=315
I?m not sure I believe the accuracy of this report as 110 dBA would be unbearable for any period of time.

On the issue of longevity, it should be noted that the 20, 30, 40 year old 2-strokes that remain running today are very primitive machines compared to the modern DFI 2-strokes. I feel that longevity of today?s engines will have more to do with the availability of the electronic components that these engines require than on the issue of complexity of mechanical systems. High quality mechanical components will last many many years with proper lubrication and care. Whether it?s a two stroke with 150 moving parts or a 4 stroke with 350 moving parts. Today?s most reliable and trouble free engines, at least in the experience of the owners polled by JD Powers, are the four strokes with the most moving parts. As both engine types now require powerful ECUs and an array of subsystems of sensors and electronic control components that will fail over time, the means of keeping these engines running for 20 or 30 years will likely have more to do with availability of these components and of the electronic systems required to diagnose them than with the additional number of moving parts associated with a valvetrane

Another consideration when comparing the older 2-strokes to today?s DFI generation is the fact that the older machines had much more lubricating oil running through them than today?s design. With hydrocarbon emissions requirements continuing to tighten, (significantly in 2010), 2-stroke engineers may well find themselves hard pressed to meet more stringent hydrocarbon requirements and continue to provide adequate lubrication for engine demands. I would say that the jury is still out on longevity of the new generation of DFI 2-strokes.

Regarding valvetranes ? I?m far from convinced that other than maybe one belt replacement, I?ll every need to touch the valvetrane on my Yamaha. I have driven many overhead cam cars well over 150K and never adjusted valves. Most have been bucket and shim setups, which by design are extremely stable and long lasting, and is what I believe is currently used in the Yamaha engines. The mechanics that I?ve talked to have usually indicated that unless you can hear one tapping, to leave them alone.

Fuel mileage ? very close, though I would wager that I could produce more test reports on like hulls with the 4-stroke having the advantage at midrange and WOT when comparing MPH/MPG, (not RPM/MPG)

Top Speed ? again very close ? On like hulls probably a slight advantage to the 2-strokes, though I can show many examples of the 4-strokes pushing a given hull a little faster.

Two strokes continue to have the edge in acceleration, weight, and midrange torque. Acceleration and weight are a consideration for some, but like myself, not so much for others. I have to admit that I confused how the E-Tec?s much touted midrange torque translates into real life benefit. Maybe if I needed to tow another boat really fast, or if one of the engines failed on my dual engine sport fisherman and I needed to plane that hull to get back fast. I don?t know, hardly everyday scenarios. Otherwise it just seems that the higher midrange torque would translate into better acceleration, which we already covered.

 

[mthieme]

Re: 2 stroke or 4 stroke?

I think we chased rebelson away.

 

[Joe_the_boatman]

Re: 2 stroke or 4 stroke?

Fuel injection is in it's infancy ????

Nope, fuel injection's been around a while ("EFI"). A family friend has a 1960's Corvette that has mechanical fuel injection.

High pressure Direct Injection ("DI", or Direct Fuel Injection - "DFI") on a 2-stroke engine is fairly new. Optimax came out, when, 1998? Multiple iterations of the Optimax, and replacement of Evinrude's FICHT w/ E-Tec, etc show that they're still working on the technology.

High pressure injectors used in DI applications have been around a few years, also (diesel engines). 2-strokes having oil sprayed in the crankcase and gas sprayed directly in the combustion chamber sounds like a winner to me, it's just that they have yet to be proven. Time will tell.....

 

[mthieme]

Re: 2 stroke or 4 stroke?

DFI on a 2 stroke engine is not new.
DFI on an outboard 2 stroke is relatively new.
I think the technology in general is proven since it has been around for decades although not widely used due to a lack of popularity.
I think outboard manufacturers are wrestling more with marketing and one upping each other given recent EPA regulations and just pure competition of a new breed of outboards. This is nothing new either.
2 cycle days are numbered, so it will all be moot soon.

 

[CATransplant]

Re: 2 stroke or 4 stroke?

On the issue of longevity, it should be noted that the 20, 30, 40 year old 2-strokes that remain running today are very primitive machines compared to the modern DFI 2-strokes.

Indeed they are, but I prefer the word "simple" rather than "primitive." One of the reasons they remain running is that simplicity. Take a 50-year-old two stroke, with a simple magneto and carburetor, and there's not much to keeping it running properly. Normal maintenance is a snap, and you can replace the entire ignition system for about $100.

Yes, they are smoky, used a lot of fuel for their output, and wouldn't fit into today's marketplace. That said, I'd much rather have a nice 40 hp OMC from the 60s on the back of my boat than any of today's 40 hp outboards. And that's just from the maintenance point of view.

I know I'm an old geezer, but I'm not talking about the "good old days" here. There's much to be said for simplicity and owner maintainability.

 

[Joe_the_boatman]

Re: 2 stroke or 4 stroke?

DFI on a 2 stroke engine is not new.
DFI on an outboard 2 stroke is relatively new.

Where is there a direct-injected 2-stroke engine outside of the marine industry? Just looking for conversation here, not an argument.

I'm researching buying a new outboard, so this is interesting to me. I was under the assumption that the OB manufacturers were coming up with most of this new DI stuff.

http://en.wikipedia.org/wiki/Gasoline_direct_injection

 

[noelm]

Re: 2 stroke or 4 stroke?

there will never be an answer to this question EVER, the 2 stroke lovers can come with an advantage over a 4 stroke, just the same as the 4 strokers can come up with an equaly valid advantage, just buy the one you like and be done with it, just like Ford and Chev or any other brand loyal "debate" it will never end (and some don't want it to!!)

 

[mickjetblue]

Re: 2 stroke or 4 stroke?

Aside from the technical aspects, there is also affordability.
I wanted more hp on my jon boat, and I bought a used 2 cycle at a fraction
what a new 4 stroke would cost. It has great torque, and very good mileage.
The exhaust fumes are rarely noticeable, and I use synthetic oil. Yep, I'm
adding the oil direct to the tank, and don't mind it. I also like the Johnson
"eagle wings" look on the motor cowl.

Whatever works better for you at the time you want it is what's best.

 

[56 rude]

Re: 2 stroke or 4 stroke?

For me its looks!I cant imagine putting a modern ugly 2 or 4 stroke motor on my antique (60 plus years) cedar-stip boat,im stuck in the 50,s for that boat as it looks just right with a 1957 johnny on there.I might also add that all my old motors run just like new and are very simple to work on and fix.