better choice 2 stroke or 4 stroke?

Luckily we do not have the emission control issues that are law in many countries, iow, we can still enjoy our two strokes.
I have the local Tohatsu outboard agency and most engines sold are two strokes. Today's two stroke do not smoke (not at all in cases) as the older stinkpots and also run quite silently. The new Tohatsu TDLI's are quite a gas and comply to all international emission standards and will run the pants off any equivalent sized four stroke.

Four strokes are expensive to keep. You have oil changes, filters and cam belts to look after and usually when something goes wrong on them, its mayor and expensive. My little backup 2S engine is usually tucked into a hole in the boat with no fear of oil spilling out, and or fouling the valves by doing so. And as said, they are not only more complicated but also heavier.

The new generation two strokes such as the Tohatsu TDLI's, are just as quite as four strokes and basically uses the same amount of fuel.

Here are some figures on the fuel consumption quoted by Tohatsu.

Two stroke 30hp - 13.0 l/h (3.4 g/h) at WOT (conventional 2S motor)
Four Stroke 30hp - 10.4 l/h (2.8 g/h) at WOT
Two stroke TDLI 40hp - 15.2 l/h (4 g/h) at WOT (latest technology)

Not much between them all although the TDLi is a 40hp. But one has to look at the bigger picture. The purchase price of a 4S can easily be about 30% more than conventional 2S. Add to that the service charges as they are much more expensive to maintain and compare running costs over 5 years ownership and one will find that 2S motors are actually cheaper to run than their 4S cousins. And they are more responsive and faster out of the hole when needed.

My 2 cent worth

 

It's not quite fair stating oil changes as one of the maintenance costs for 4 strokes, while completely ignoring the fact that the oil that is mixed into the fuel of 2 strokes add's about 10% on top of the fuel price.

As we say in Holland: that's comparing appels and pears.

Besides that, the difference in fuel consumption between 2S and 4S is the smallest at WOT. At 50% throttle, the differences will be bigger. And engine's aren't run at WOT all the time in real life, so comparing WOT consumption, is biassing the 2S.

I'm not saying 4 strokes are always better. Like I said, I owned a 2S for ages, on a small ski boat, where it excelled. But for quiet cruising in a small displacement boat, a 2S does not even come into my consideration.

 

2 stroke vs. 4 stroke

Loopers must be rebuilt more often than cross flow but are far more efficient, less fuel lost through exhaust. I rebuilt my racing powerheads (loopers) once/season but would have been able to run one for years with ordinary use. If you want top performance then there's a price. Oars, e.g., can last for a lifetime ... .

 

dont forget the pollution your waste oil and filter makes from your 4stroke not to mention all the extra pollution in trying to make the thing with a gazillion more parts and if it goes wrong will probably be a throw away due to the cost like everything else Japanese.

 

2 stroke V/S 4 stroke

If I was to run an E tech or TDLI 2 stroke and my pal was to run a Honda or Yamaha 4 stroke under typical conditions which (2S-4S) would require the most lube oil to operate? Me or my pal?

Easy Rider

 

Well, that's not possible to answer properly without a lot of assumptions:

1. This is not a retorious question.
2. You and your pall both have a 50 hp engine.
3. You live up to your name and you are a true "Easy Rider". Your fuel consumption equals 10 ltrs / hour.
4. Your 2S fuel is mixed 1:50.
5. You opperate your boat 100 hours a year.
6. You service your engine once a year.

At the end of the year, you have used up 100 x 10 = 1000 ltrs of fuel. That means 1000 / 50 = 20 ltrs of 2S lube oil.

Your pal with the 4S will have had one oil change, which varies on the size of the engine and the make / model. But let's say just over 2 ltr for a 50hp. So that's 10% of your oil consumption.

I don't know what oil costs, but over here that would round up to about EUR 180,- in savings. Of course then there is the fuel economy, which for an Easy Rider could easily be around 30 - 40%.

The 4S will be more expensive to service they say (no valves, etc.), maybe that's true. The 2S will have been cheaper, but that's only until it wears out it's pistons, and the price of 2 or three of those for a 50HP, even aftermarket, will hurt.

 

2 Stroke / 4 Stroke

Two huge flaws in your post
1 One should have 2 or 3 oil changes in a season. My Suzuki DF60 4 stroke specs lube oil change every 6 months or 100 hrs. With a 5 US quart capacity that would be 2.5 gallons per year. But since they try to minimize the maint schedule as a sales feature I'd say 3 changes per year are a good idea.
2 You are using Max oil consumption for the 2 stroke and they only use a fraction of that. In full throttle operation on an injected 2 stroke the oil ratio is somewhere between 20-1 and 50-1. At cruise throttle it's probably around 80-1 and at idle perhaps 150-1 to 200-1. If you had an underpowered boat it would be higher and w an over powered boat and a light load much lower.
Easy Rider was the name of the only boat I have designed and built.

Easy Rider

 

Two strokes are lighter in weight and more responsive. Depending on the app. If you have a boat that does not require performance like a house boat I'd consider a 4 stroke. If you have a boat that you want fast and furious then go for the 2 stroke.

The new two strokes are much better on fuel than the older ones. I had a 115 which was heavier on fuel than the newer 200's. They also don't smoke like the old ones do.

Personally I like the 2 strokes. They never die.

 

[qoute]
2 You are using Max oil consumption for the 2 stroke and they only use a fraction of that. In full throttle operation on an injected 2 stroke the oil ratio is somewhere between 20-1 and 50-1.


I have never seen a stock oil injected two stroke us a ratio richer than 50-1.

 

Strokes

May have been thinking of motorcycles. They have a much more sophistaced oil injection system as they have high rpm low load conditions. Outboards have (I believe) throttle position or engine speed function only while in motorcycle injection systems several variables control the amount of oil injected. I know some motorcycle injection systems at WOT and 7000rpm or more will inject at a 20-1 level. Some motorcycles inject oil at several locations also. Outboards are much simpler. Sea water cooled outboards run so cool more oil than 50-1 is not needed so since I'm not knowing all the specs and details I said 20-1 just to be safe. Should have said about 50-1.
Another point. With 4 strokes many (possibly most) don't keep track of their maintenance schedule or just don't bother to change oil when needed. Two strokes always feed clean oil where it's needed.

 

Several variables for motorcycle oil injection???

You mean a cable splitter? one cable goes to the carb and the other goes to the oil injector.

Plus you argument has one massive flaw, your 2 stroke oil ends up being spit out the back into the air we breath for us all to enjoy. Or worse ends up spit out under water---nice.

The 4 stroke keeps mostly all of it where it can be changed and disposed of.

 

The 4 stroke still emmits it's poisenous exhaust gasses through the prop and in the water to muffle the sound. I doubt there is a big difference. The new 2 stroke engines runs at 100:1, which makes it much less oily.

Never the less, we need a motor without any poisenous gass or anything else emissions

 

Thats right Fannie but the 2 stroke oil system is a total loss system.

--ALL-- of its oil after one time lubrication is dumped in the exhaust.

As you know!!

Now if some one could design a kind of separator in the exhaust and circulate it back to the tank, or even a holding tank for disposal !!!!!!!!.

 

I would give my 4 stroke engine just one oil change at the end of the season if I used it a lot and the color of the oil urges me to change it. If it looks healthy, I would just change the filter. Modern synthetic oil maintains its properties for years and 100's of service hours. A head of research from Shell told on Dutch TV after his retirement that there is no need to change oil at all, just the filter. It caused a lot of commotion at the time and his former employer somehow succeeded to keep him from repeating his statement.

If my college or friend would use a 2-stroke engine I would threaten to throw my used oil overboard in his presence and explain to him that is what he is doing every time he uses his boat.

 

Easy Rider,

1. I was using 50HP engines in my comparison. There's no 50HP with a 5 US quart capacity. 2.1 - 2.5 is normal. Also, where I live, the season is from early june till mid-september. No-one changes the oil halfway the season (unless there has been a mechanical problem and it has been contaminated with water). So estimating something around 2 ltrs is fair in this comparison.
2. Fair enough. Let's assume it's 1:100. Still 5 times the oil consumption of a 4S.