2 stroke vs 4 stroke and other newbie questions

[Hagopm]

Hello All

I have just moved to Bournemouth so am thinking about getting a powerboat for pootling around. I'm planning to do the RYA Powerboat level 2 course. I've started looking at used powerboats on ebay and also PWCs. Seen some bargains for £1500 - £2500 and would like to setup a boat share with 2 or 3 other people as I would realistically only use the boat 2 or 3 days a month and would need to share costs.

I try to be environmentally friendly so am keen to take the least polluting route. I did some research recently and read that 2 stroke engines only burn about 75% of the fuel you put in them, the rest is pumped out into the ocean unburnt which causes terrible pollution, damages habitats and kills fish.

So it would follow that a four stroke engine is more environmentally friendly as more of the fuel is combusted. More and more PWCs are being made with 4 stroke engines nowadays and 2 stroke engines have been banned on many lakes because of the pollution they cause.

I assume that most outboard engines are 2 stroke especially those found on used boats in the 70 - 150 hp range? Is it realistic to have a 4 stroke engine in this side?

Opinions welcome please on the most environmentally friendly way to conduct a powerboat!! Thanks.

 

[longjohnsilver]

Hello and welcome to the forum.

An interesting first post, I'm not sure that I agree with your conclusion that 2 strokes cause terrible polution, damages habitats and kills fish. Not seen much of that happening in my 30 years of boating. Modern 2 strokes are imho just as efficient and evironmentally friendly as any 4 stroke, don't forget that with a 4 stroke you still have engine oil to dispose of. However over the past 10 years I would say that in your 70 - 150 hp range there are just as many, if not more, 4 strokes than 2 strokes. Admittedly much older outboards are more likely to be 2s, and some of those will not be particularly efficient and because of their age, not as reliable.

However I know nothing of engines that PWCs use, others might be able to help you there. But with your budget I suspect you will be looking at quite old boats with much less choice.

Good luck with the search.

 

[wipe_out]

Welcome to the forum and to Bournemouth, a great place to live..

2 stroke outboards were very popular and very inefficient 20+ years ago.. Then 4 stroke gradually took over and today probably 90% of outboards are 4 stroke.. In that time 2 stroke technology also moved on and the new 2 strokes like the Evinrude e-tec are claimed to be as efficient as 4 strokes.. Personally I have no issue with either as a technology and spent many years tuning and modifying 2 stroke motor bikes in my teens and 20's.. On a boat however I would definitely prefer 4 stroke over 2 stroke especially from an environmental standpoint.. Certainly if the environment is a concern then you probably want to stay away from older 2 strokes in favour of similar aged 4 strokes..

Of course for the ultimate environmentally friendly "power" boat there is always a Kayak or Paddle Board?

 

[Vitesse]

With a lower budget you will be looking at older outboards, generally 2 strokes. Have you considered sailing?

Beware of eBay bargains. If you can get a boat share set up that might best. Try and find someone who's into boats rather than an angler, for whom the boat is merely the means to get his hook in the right place.

 

[Canopy Locked]

On a boat however I would definitely prefer 4 stroke over 2 stroke especially from an environmental standpoint..

I'd have to disagree with that.

Certainly the old style 2 strokes were not the best of engines, but the modern 2 stroke is a very different beast.. Below is a copy & paste from the BRP (manufacturer of the ETEC Evinrude) website.

BRP's Evinrude E-TEC direct injection 2-stroke outboard engine use 75% less oil than traditional two-strokes and 50% less than traditional direct injection systems. They release only one-fifth of the carbon monoxide emissions of a four-stroke engine at idle and are compliant with stringent U.S. Environmental Protection Agency (EPA), European Union (EU), and California Air Resources Board (CARB) 3-Star ultra-low emissions standards. http://www.brp.com/en-gb/innovation/eco-performing-technologies/2-stroke-engines

As far as pollution is concerned... I don't think that it would be correct to say that they do more damage to the environment!

 

[Montemar]

I think that 2-strokes are lighter than 4-strokes. 75% of fuel is unburned seems incredibly high though some lubricating oil is burned along with the petrol. An air to fuel ratio of 100:1 seems common and not too bad but less than this and you will notice the fumes and if you don't your wife will! I had a 60hp Mercury with a mix in the engine system which was easy to use and very reliable.
I recall the now defunct Motorboating Monthly magazine ran a test on small 4-strokes with one 2-stroke as a reference. The 2-stroke did very well!

 

[wipe_out]

I'd have to disagree with that.

Certainly the old style 2 strokes were not the best of engines, but the modern 2 stroke is a very different beast.. Below is a copy & paste from the BRP (manufacturer of the ETEC Evinrude) website.

As far as pollution is concerned... I don't think that it would be correct to say that they do more damage to the environment!

We completely agree that modern 2 strokes have improved enormously and I did say that in my post.. I also mentioned the Evinrude etec..

As for the quote from there website the issues are first that it is from BRP and it is marketing, they are hardly going to say where they possibly fall down on the emissions front.. For example what gasses and pollutants caused by burning the oil?.. Secondly is that they specify the emissions level at idle in their claim of the CO output, that's all very well but what about right through the rev range where the engine is usually operating? As the air/fuel/oil velocity increases through the engine what happens to the emissions numbers?

As I also said I have no issue with either technology and would happily buy a boat with a modern version of either engine, I simply "prefer" 4 stroke over 2 stroke for an outboard if I have the choice..

Now on a motocross bike give me a 2 stroke any day..

 

[Stats007]

More marketing from Honda here but you get the idea...

If large capacity 2-strokes were so great the likes of Honda, Suzuki and Yamaha would still be making them.

I personally wouldn't ever buy a another boat with 2-strokes fitted - purely on the basis that the market for resale is so limited.

 

[CLB]

More marketing from Honda here but you get the idea...

If large capacity 2-strokes were so great the likes of Honda, Suzuki and Yamaha would still be making them.

I personally wouldn't ever buy a another boat with 2-strokes fitted - purely on the basis that the market for resale is so limited.

Pedant mode on..... It's a little known fact that Honda has never made a two stroke outboard.

 

[Hagopm]

Thank you very much everyone for your opinions!

 

[ontheplane]

For your budget I say ignore the 2/4 stroke issue - will be far more important to just get something in decent nick and reliable

 

[l'escargot]

In that price range, I would think you are unlikely to find a reasonable set up with a decent 70 to 150hp four stroke engine so you are looking two stroke. I doubt whether an Evinrude etec will come in budget so go for a older fuel injection such as the Yamaha autolube. Avoid the older premix engines like the Force, they drink fuel at a ferocious rate.

 

[spannerman]

We completely agree that modern 2 strokes have improved enormously and I did say that in my post.. I also mentioned the Evinrude etec..

As for the quote from there website the issues are first that it is from BRP and it is marketing, they are hardly going to say where they possibly fall down on the emissions front.. For example what gasses and pollutants caused by burning the oil?.. Secondly is that they specify the emissions level at idle in their claim of the CO output, that's all very well but what about right through the rev range where the engine is usually operating? As the air/fuel/oil velocity increases through the engine what happens to the emissions numbers?

As I also said I have no issue with either technology and would happily buy a boat with a modern version of either engine, I simply "prefer" 4 stroke over 2 stroke for an outboard if I have the choice..

Now on a motocross bike give me a 2 stroke any day..

The reason the New Evinrudes use so little oil is that its not mixed into the fuel and burnt as in conventional 2 strokes. Its injected into the lower crankcase under the piston which is where the lubrication is needed, therefore less required as its introduced exactly where its needed, and only a small amount passes through the transfer ports and is burnt in the combustion chamber. Hence the cleaner exhaust and drastically reduced amount of oil consumed.