Again, Evinrude only. Do you work for them? Manufacturers will always go for the least expensive way to do something, as long as quality and operation does not suffer.
Outboard operation improved by leaps and bounds when they went to 4-stroke. Are they more expansive to produce than old-school 2-strokes? OH YEAH! Or it would have happened much earlier. And emissions was the biggest impetus to go to 4-stroke. It had to be done SOON. 4-stroke was the answer.
Now here is Evinrude, back from the dead. (I guess the other half of OMC, Johnson still is..). They needed a trick to prove they are still here. A 2-stroke that is powerful and clean, and starts on first kick. But I bet it cost them BIG....

 

None of them need to meet the emissions standards automobiles do, Nor do outboards. When I see 2-strokes in cars/trucks again, they will have full credibility in my eyes. If they were indeed as clean/efficient as 4-strokes, the automakers would drop the 4-stroke like a hot potato and run with the 2-stroke. But that is not happening.

 

Meanwhile, back at the ranch... if you aren't subject to automotive emissions laws and want a boatload of torque at 3200 RPM, combustion on every crank rotation seems like an avenue worth exploring.

 

And in case anyone else was curious about the bus engines...

https://en.wikipedia.org/wiki/Detroit_Diesel_Series_71

 

You clearly have no idea what you are talking about, why keep making **** up?? I've already proved your claims wrong, so now you are trying to move the target to automotive emissions, when you still can't even come up with a bsfc for "efficient" or "suck fuel"

The original topic, and Lances question is the perfect situation to use a 2 stroke. He needs lots of torque at low rpm.

My vote is to run the cam 1:1 Its going to take an expensive valve train, some big ports/valves on the exhaust side, and piston cooling/TBC coatings.

pd blower and turbo(s) or just a blower? Getting it to start will be tough any other way

 

Awesome thread, hopefully you post your progress. Outboards went to 4strokes purely due to pressure from the government over emissions since an outboard dumps its exhaust into the water and the thought of oily exhaust gasses in the water made environmentalists flip. When they did, engines became much bigger, and much weaker for a given size. My father has an early 90s 150hp V6 Evinrude 2stroke outboard that is over 100bs lighter than a modern 4stroke 150hp. When hanging off the very back of a small boat, 100lbs is a huge difference.

I rode 2stroke dirt bikes in the 90s and currently build and mod tiny 49-80cc 2strokes for use in motorized bicycles as another hobby and they are a ton of fun but are a whole different beast. Not sure where the efficiency and negative arguments are coming from since as far as HP per ci and HP per lb they far exceed 4stroke motors. Power density is not even on the same planet. While seemingly very simple though, things like tuned exhaust chambers, port timing, piston windows, piston skirt mods, and reed valves are all parameters that need to be taken into consideration that are either inapplicable or not nearly as important as on a 4stroke...but the payoff is massive once you get it to work right. In the 1930s there were giant 2strokes north of 2,000hp that could pull whole trains to 60+mph. This was almost 100 years ago!!! Glad to see Evinrude still pushing the boundaries since it's a shame so much of the market stopped R&D for so long on them due to tightening emissions and lots of bad press. For powersports like motorcycles, boat racing, snow mobiles, etc they are unrivaled even after 30+ years of stagnation.

Sounds like this is the perfect use for one, and I had no idea this was even possible. I figured you would need lots of cylinder and port mods to make it work effectively.

Thanks for sharing.

 

I too am glad 2-strokes are coming back. As said, for power density they can't be beat. And it looks like the emissions picture for them IS improving. That is what killed them in outboards and road-going bikes a while back, as emissions technology had not YET caught up. This is also why Detroit Diesel abandoned 2-stroke diesels back in the '90's. I doubt they will be back, but we'll see about lighter duty automotive engines. So far Evinrude is the lone player in mass market outboard engines.

 

2 Stroke is more efficient then 4 stroke and the answer lies in the 2 and 4... its just all about how you do the testing as only one variable can be to prove your findings

If you want to talk to a 2 Stroke guy, speak to Blair (Gordon P. Blair)