So How is a Four Stroke so much better than a Two Stroke?

[Capt. Bob]

OK,
I've laid off this gas cooling thing but in reality, fuel mixture cooling does occur in 2 strokes (and in 4 stokes too). Granted it is minimal but it adds a factor into the overall performance of the motor, even if slightly.
That stated, I think we all agree that whether it is a 2 or 4 stroker, the main cooling component is water in dealing with an inboard/outboard propulsion device.

[Circle Hooked]

Calamin lotion may help.

[Capt. Bob]

...plus I came back with some sort of body itch that I'm dealing with.

He is itching all over. He was in an epson salt bath when we spoke.
[/quote]

Well unless he's swollen I suggest he place himself in an oatmeal bath instead.

Trust me, I'm not licensed to practice in the State of North Carolina.

Or anywhere else for that matter but.....

I did have Chicken Pox at the ripe old age of 47.

[Circle Hooked]

I was just told a warm bath with green tea leaves

[GoneFission]

For the sake of discussion though, a few two stroke facts:

Two strokes have a rapid wear zone in their cylinders.
Two stroke pistons run hotter.
Conventional two strokes are gasoline cooled.
Two strokes actually do have an intake and exhaust cycle.
Two strokes do have valves.
And, two stroke outboards have more moving parts than a four stroke. Figure that one out.

OK, time for a fact-check:

Wear zones - depends on cylinder base material, rings, and piston material and clearances.  Remember Detroit Diesel truck engines are 2 strokes and seem to run a really long time...  

Runs hotter - depends on piston cooling and compression ratio.  High compression engines have higher piston temps, but usually have oil jet cooling on the bottom face of the piston.  4 strokes are normally higher compression than 2 strokes, but 2 strokes fire twice as often.  

Two strokes are gasoline cooled - then why do you need a water pump?  Sorry, this one does not pass the snicker test.

Two strokes have an intake and exhaust cycle - so do rotary engines, miller cycle engines, and every other gas powered engine - cuz you gotta bring the air in a force it out.  But the intake and exhaust in a 2 stroke happen in the same turn of the engine and the cylinder fires on every RPM.  Four strokes (Otto cycle) fire every other RPM.

Two strokes have valves - yes, they have reed valves to prevent back-feed into the crankcase.  These are passive valves, not articulated by a camshaft.

Time for a check of the facts in the fact check.

Wear zones. So did you support or deny that fact? It's not really clear.

Pistons run hotter. Again not really sure from your response. Keep in mind we are talking about outboard engines here.

Conventional two strokes are gasoline cooled. I'm not sure what a snicker test is but notice that I did not exclude the water pump or the water cooling, only stating that they are gasoline cooled. If you deny that they are I'd like to hear a good reason for discussion.

Two strokes have an intake and exhaust cycle. I see you agree with me on this one.

Two strokes have valves. I see you agree with me on this one as well. I'm not sure what a passive valve is as opposed to an active one, or what you mean by articulated, but we agree on the valves issue. I've often heard it claimed that they do not have them which is why I brought it up.

Two strokes have more moving parts. I see you steered clear of that one.

Seriously there is some pretty good and interesting discussion material here if anyone is inclined. It may help to establish a more informed opinion with regard to the 2 stroke/4stroke debate.

Boatdood - gotta give you credit - you are persistent!!!    Ever think about going into politics?    Maybe you could go to work for Obama and convince everyone the economy is really OK!  

[Boatdood]

Allright guys. I'm almost afraid to wade back in here. Well, almost. Fitz, I really didn't mean to offend. I'm just a lighthearted guy and it seemed like good fun. Part of the problem with the internet is that we are limited to the spoken word, and with that limitation we don't always see the other's intent, or the silly smile on their face when what they write is only a joke. You were right though. 17 posts is not nearly enough to poke a little fun with someone who is itching all over. Man what is up with that itch though.? My wife watches too many TV shows about weird things people catch from foreign countries.

For the guys with two stroke outboards who I might have offended. I really don't think your outboard is a weed eater. That was a joke. Light as they are they are still too heavy for weed whacking. My intent was to stir up the emotions a bit though and get the conversation started. How many people would have been motivated to even respond if I said, Heh, a two stroke is just as good as a four stroke, or the other way around? Who wants to talk about that? Chevy people get fired up though when I say something like, I went to give a guy a jump and had to look in the owner's manual to open the hood. I have a Ford and don't need to do that often. We all have what we can get and we tend to be proud of it, whether it be an old two stroke outboard or a broken down Ford. For the record I do not own a four stroke outboard, but I do own several good old two strokers. One of my favorites is an old 5 hp Johnson my dad and I used to fish with. Great memories go along with that engine and I'll never give it up, although I may give it to one of my boys one day.

That being said though can we get back to the discussion?

Marketing guys plant a lot of beliefs in the minds of would be consumers. Some of it is true, and some they want us to believe is true. They didn't miss out on the outboard debate by any means. Some of the claims they made were aimed at one or the other of the engine designs, depending on which stroke they were charged with promoting. Since four strokes pretty much took the new engine market by storm starting in the late 90's the two stroke guys were caught playing catch up. They did what they could and pointed out the obvious. Four strokes were definitely heavy. They were painfully slack on the bottom end. And they were a bit more complicated, so the marketing strategy was aimed at exploiting those shortcomings, and maybe even implying a few more. The unfounded implications in part were:

They can't stand high speed operation like a two stroke can.
They have more moving parts.
Upkeep will be like a kick in the, well you know what.

I say unfounded because now a decade or so later they have proven to be quite acceptable at the RPM's they need to turn, they actually do not have more moving parts, and if you can change oil and plugs occasionally they aren't really all that expensive or complicated to keep up, but the battle for market share goes on and myths die hard.

I made the list of two stroke facts to promote discussion. Unfortunately my prior remarks illicited more anger than thoughtful discussion, so a for instance of what I'm getting at.

Gasoline cooled. We all know that both two stroke and four stroke outboards for the most part are water cooled so what's up with this claim? In conventional two strokes the gasoline enters the crankcase and flows into the combustion chamber from there. On the way through it cools everything it touches through evaporation and by simply being cooler than the machinery it comes in contact with. It does the same thing in a four stroke admittedly but there's a reason I brought this up. The early DFI two strokes were extremely problematic, in great part due to this loss of gasoline cooling primarily in the crankcase. Crankcase temperature went up dramatically while we still had the same oil to lubricate the internals. That oil wasn't up to the task with regard to the new temperatures they had to work in. Catastrophic engine failures were common as a result, which opened the door to the new four strokes, even with all their shortcomings.

Admittedly this might not be interesting to everyone, but I think it's pretty neat stuff to know. It took me a couple of years to figure this out by the way, so I'm not really a know it all.

[gran398]

Hey...its all good, as the kids say.

I know your son...he's a fine man. You should be justifiably proud.

You're used to the chatter on THT. And that's cool...but personally...have never made a post there. And won't.

I'm really happy here at the Clubhouse. It's all about helping each other. Based upon outside input, as they come aboard ...we have the best boating forum on the net.

Yep...you've re-hashed a topic that has been covered, been discussed...and beat to death. As the two-strokes and four-strokes become closer and closer, nearly inseparable...perhaps its time to introduce something exactly in between, a fair compromise, "Change we can believe in"....

 The three-stroke

[slvrlng]

Gasoline cooled. We all know that both two stroke and four stroke outboards for the most part are water cooled so what's up with this claim? In conventional two strokes the gasoline enters the crankcase and flows into the combustion chamber from there. On the way through it cools everything it touches through evaporation and by simply being cooler than the machinery it comes in contact with. It does the same thing in a four stroke admittedly but there's a reason I brought this up. The early DFI two strokes were extremely problematic, in great part due to this loss of gasoline cooling primarily in the crankcase. Crankcase temperature went up dramatically while we still had the same oil to lubricate the internals. That oil wasn't up to the task with regard to the new temperatures they had to work in. Catastrophic engine failures were common as a result, which opened the door to the new four strokes, even with all their shortcomings.

This is some pretty neat stuff!

  I think its the smell, When you crank up early in the morning and all the mosquitos run the other way.The two people on the dock start backing away. The guy coming in slams it in reverse and backs out, I mean how can a fourstroke compete with that.
  I for one am going to run the one I have until it blows. At that time I will see what is available, and then make a decision. Hopefully by then there will be a outboard that burns seawater. Hey Boatdood, is your five like this 5.5? Its going on 55 years old and sounds like a clock ticking at 1200 rpms. If the 175 I have lasts like this motor maybe the motors of that time might actually burn seawater!

 

[slvrlng]

Is a 3-stroke like a Wankel?

[Boatdood]

Lewis, my five is a bit different than your motor there. I have one like that though, only a year or so later model. Mine has the one piece cowl and a fuel pump instead of the pressure feed yours has. My five is a direct drive, no gearshift, with 360 degree steering. We used it mainly for trolling. I'd sit on top of the big motor and steer this one with my foot. It has a friction throttle handle separate from the tiller handle so we could set the speed and leave it. When a fish would hit I could kick it into a quick turn and work back to pick up the fish without missing a beat.

[Capt. Bob]

Is a 3-stroke like a Wankel?

 No,
 but Scott's like a Wankel in they both contain eccentric parts in their operation :shaking2:

Come to think of it, there are quite a few of us "wankels" on this Forum, thank you very much.

As far as three strokers are concerned, that's a completely different forum.  :o

[MarshMarlowe196]

For the guys with two stroke outboards who I might have offended. I really don't think your outboard is a weed eater. That was a joke. Light as they are they are still too heavy for weed whacking.

     

Is a 3-stroke like a Wankel?

No,
but Scott's like a Wankel in they both contain eccentric parts in their operation :shaking2:

Come to think of it, there are quite a few of us "wankels" on this Forum, thank you very much.

As far as three strokers are concerned, that's a completely different forum. :o

     

I think its the smell, When you crank up early in the morning and all the mosquitos run the other way.The two people on the dock start backing away. The guy coming in slams it in reverse and backs out, I mean how can a fourstroke compete with that.

Very true Lewis.  Some of my fondest memories are fishing with Pops so early in the morning there's still fog on the water.  Backing that old 70's boat (The brand was "Happy Traveler", and it was true) with the 50hp Johnson down in the water,  waiting for it to clear it's throat with all the coughing and sputtering,  then you smell the 2 stroke oil burning and know it's gonna be a great day.  That smell is burned into my memory.  

[gran398]

Is a 3-stroke like a Wankel?

Tags: Milk Duds, Wankel, Johnson 5, three stroke, buttercorn. Search:


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[seabob4]

Boatdood,

Ahh, the days of the early Ficht motors.  If they didn't blow up, they ran awesome.  Hung a pair of the first Ficht 150s on a 245 Explorer w/upper station we used for fishing tournaments. We'd run 20 miles out, troll all day, run back in, then run up the ICW from Whitfield (the old Holiday Inn with the marina on Tamiami) to Palmetto, and back, and not even burn a 1/4 tank of gas.

I was at Hydra-Sports briefly in '99, working for Todd Biddeson, left to go back to Wellcraft/AS just weeks before the H-S plant shut it's doors due to the OMC bankruptcy declaration.  We had a ton of pre-wired, pre-built OMC panels at WC, all us electricians were called to the white house to advise engineering how to swap them all over to Merc/Yamaha...

Yeah, I remember the early days of DFI motors.  Ever try to get the cowling off an early Merc DFI (forerunner to the Opti) while standing in the splashwell?

[wingtime]

My girlfriend says she prefers four stokes over two strokes.