2 stroke vs 4 stroke 115hp

[Cujet]

Originally Posted By: abycat
No a 2 stroke has a higher Rev limit and makes most power at high revs. Both tq and hp. a 4 stroke makes its power at a much lower rpm. 2 strokes make more power with a smaller displacement than a 4.


From a technical point of view, high performance 2 strokes typically do not redline at as high an RPM as a typical modern 4 stroke. The examples are to numerous to list.

One good example for technology comparison is a 250cc motocross or Kart engine. As produced, the 2 stroke runs to 9500 RPM and the comparable (albeit less powerful) 4 stroke runs to 13,500 RPM.

In race trim, a well prepped, modded 250 2t will run to 10,500, but torque drops off sharply starting at 8500.

Whereas, a stock 450 4t will run to 11,500, considerably higher than a race 250 2t.

 

[Mik]

They have to run the cammers at a higher rpm, to compensate for their lower torque production (and still generate decent hp numbers).

In terms of dirt bikes, let the two-strokes and four-strokes run equal displacement and watch the cammers disappear from the market quicker than a sundae on a hot day...... The only way cammers can hope to be competitive is by enjoying an overwhelming displacement advantage...... Modern DI and computer engine management tech have, for all practical purposes, done away with the two-stroke's historic weaknesses.... shame the masses have been brainwashed by the likes of Honda and don't see it........

 

[hattaresguy]

Two stroke, 4's don't have the punch.

4's are better motors to live with, I wouldn't go back to the old 2's for anything. I do miss the smell though!

 

[fsskier]

There are a lot of nice 4 strokes on the market, but none have the torque and power to weight ratio of a modern two stroke. Google "60 person record pyramid" and see the world record easily pulled by Evinrude two strokes. No, there is no longer any two stroke oil smell, the new Evinrudes do not mix any oil into the gas at all, a pressure fed crankshaft provides lubrication just like a 4 stroke.

I personally often pull 30 or more skiers with evinrudes
www.5sst.com for pics.
The ski show teams that tried 4 strokes have now replaced them with 2 strokes
4 strokes are great for pontoons and non performance hulls..

 

[Tuffy1760]

Pulling skiers is all about the prop... a lower pitch prop is needed...
4stroke...2stroke... its all about the prop

 

[lars11]

I have not compared say a 150 2stroke to a 150 4stroke outboard, but did compare a 170hp volvo penta inboard to a 175 2 stroke merc outboard and the 2stroke was like a horse-kick in the butt compared to the slow inboard. Some of that could be crank power compared to prop power rating but...

Still, academically, I look at a torque curve from a modern 4 stroke and it should have more pull from start, i.e more hp at low rpm.

let someone do a drag race?

 

[CT8]

I would buy a 2 stroke just because.

 

[Clevy]

In the hike world,quads it takes 450cc 4 stroke to equal a 250 2 stroke. A 2 stroke feels more snappy,instant response. A 4 stroke feels a bit slower to rev.
In my youth we rode 2wd quads like the banshee and the 250 2 stroke versions were quicker though maybe not faster

 

[philipp10]

Originally Posted By: lars11
I have not compared say a 150 2stroke to a 150 4stroke outboard, but did compare a 170hp volvo penta inboard to a 175 2 stroke merc outboard and the 2stroke was like a horse-kick in the butt compared to the slow inboard. Some of that could be crank power compared to prop power rating but...

Still, academically, I look at a torque curve from a modern 4 stroke and it should have more pull from start, i.e more hp at low rpm.

let someone do a drag race?

it's the weight reduction your seeing there. Taking 300lard [censored] puonds out of your boat can do wonders.....



it's the weight reduction your seeing there. Taking 300 lard [censored] pounds out of your boat can do wonders.....like leaving your friends fat wife at the dock.

 

[SteveSRT8]

Originally Posted By: fsskier

The ski show teams that tried 4 strokes have now replaced them with 2 strokes
4 strokes are great for pontoons and non performance hulls..


That right there says it all. The 2 strokers cannot be beat for low end torque...

 

[gonefishing]

I'm certainly no expert but I have always heard that 2 stroke outboards have better hole shots then 4 strokes. I think this gap has narrowed over the years with lighter and better 4 strokes (variable valve timing etc.). I have seen a few Evinrude E-tec power curves and they show more torque lower in the RPM band when compared to competitors 4 strokes.

Either way the outboard industry seems to be focusing on 4 strokes with the Evinrude being the exception (no 4 strokes and a new 2nd generation Etec released this year). Suzuki and Honda only offers 4 strokes and Yamaha seems to be getting away from them (I think their HDPI line of 2 strokes is or has been disconnected). Mercury still has a mix of both.

 

[ironman_gq]

Holeshot has more to do with the prop than the motor. In my experience, the 4-stroke motors are great for most people. They can sit and idle all day long without loading up, start everytime and don't smoke or stink, no gas to mix or injection oil to check, spark plugs last nearly forever as well. The biggest pain is the annual OCI which really isn't a problem at all. They also sip fuel at low speeds compared to a 2-stroke although at WOT they are nearly as thirsty.

2-strokes are lighter, louder, and the exhaust has that all familiar smell. The new ones are much cleaner than the old ones but the characteristics are there. They are good for boats that live at WOT and/or need to be lightweight.

For any of the new motors (larger ones especially) the electronics are going to be the biggest headache and cause more trouble than anything.

 

[lars11]

And don't forget that 4 strokes generally have timing belt changes to deal with.
But, the new 4 strokes are super nice to run. tried a 20 ft WA with a 100hp Honda this weekend and what an engine! Wonderful.

For most boats I would pick a 4 stroke, except two scenarios: Small boats sensitive to weight and infrequent use boats that you just want to start and run once in a while and want to avoid too much scheduled maintenance.