Difference between 4 stroke and 2 Stroke Outboards

[macd]

It is they who insisted on using massive two stroke engines in America's freshwater lakes, with with half their fuel, gallons a day, going unburned straight into the lakes. That is what I understand started the two strokes bad, four strokes good campaign.

I've told you a million times that 'half their fuel' is something of an exaggeration.
Two-stroke engines aren't massive. That's what we like about them.
The clampdown on two strokes began when the people of Los Angeles noticed their air wasn't actually breathable, and spread from there. Very little commuting was done by jet ski at the time.

 

[CreakyDecks]

"Massive" in terms of engine power, not physical size. I have read that tests showed them dumping two gallons of fuel an hour into the water. In the sea that might be a drop in the ocean but in a lake, however big, it's totally unacceptable. (I'm not arguing about whether that figure is true but it seems that the powers that be believe it.)

 

[Beamishken]

I think things are getting a bit out of perspective here the op asked if there would be a day & night difference between a 5hp two stroke and a 5hp 4 stroke & the answer is No there isn't a massive differance at that size both have there benefits & downsides but if the op has a reliable 2 stroke that suits his needs then swapping for the sake of it will give him little benefit if any
incidentally if a 5hp is dumping 2 gallons per hour I'd say it has a problem

 

[CalicoJack]

When we brought our last boat it came with a 3.3hp Evinrude 2 stroke for the Avon dinghy. I stupidly was tempted and subsequently brought a new dinghy which came with a 5hp Suzuki 4 stroke. The thinking behind this, if that's the term, was it was a brand new engine with a warranty, where as the Evinrude was quite old and with an unknown record. I sold the old Avon and for a while I had two engines, so I could do some comparisons. On the inflatable the Suzuki struggles to get on the plane with two adults, the Evinrude succeeded every time, although it did take some time. We also have a 14 foot Shetland open fishing boat, which we have used a GPS from. The Suzuki manages 5 knots, whilst the Evinrude used to achieve over 7 Knots and went like a train down the waves.

Nothing wrong with the Suzuki,it runs fine, but it is heavy. I have to use a block and tackle to lower it into the transom of the dinghy, rather than just hand it down as we used to do with the Evinrude.

As a bye the bye, I have had 2 strokes since I was a kid (BSA Bantams to Seagulls) and have never had a plug foul. Thrash the engine regularly,& mix the fuel carefully seems to be the message. As for fuel consumption, the only time I noticed it was when I borrowed my mates Kawsaki 750 triple 2 stroke. God was I glad when I had to stop to buy some more fuel. What performance, in a straight line!

 

[Seajet]

This thread is increasingly bizarre, especially posts 60-62.

Everyone knows UFO flying saucers are 2-strokes, you have to put your foot on the rim to start them.

 

[Cappen Boidseye]

Having seen a lot of folk on this thread slagging 4 strokes, I have a four year ols Suzuki 2.5 hp for my tender. It got dunked a week after I bought it and I got the boat yard I bought the thing from to clean it out. Four years on and it still starts on the first pull, choke on for about five seconds after the start then pushed straight back in. It runs great, I can't fault it. Now it has finished four seasons I am thinking about giving it a service, it must be due for it's first one by now! The oil in the sight glass is still clean and has never needed topping up, it still has the original spark plug. Yes if I leave it on it's side (the correct side) in the back of the car for a week or so I have to stand it upright for ten minutes while I get the tender ready, or it will not pull, however once the oil crawls back down into the sump the thing starts instantly. Maybe modern 4 strokes are heavy, it isn't as heavy as my old seagulls were, also it starts when I want it to, which is nice!

My experience with 2 strokes is with Seagulls (Aargh!) which didn't like to start in the rain, or at any other time. Oh and chainsaws, I have an 81cc Husky whch I haven't managed to start for three years now, oh and strimmers, etc. etc. etc. 2 strokes don't start, then when they do they don't idle well or reliably, foul snd smelly creatures so they are.

However, I suppose there must be quite a weight difference between a 10hp 2 stroke and the equivalent 4 stroke which could be very important.
I know that single handed I won't even attempt to get my wee engine off the tender and onto the yacht, but part of that is because me in the very stern of the tender (weighing over 21 stone with bad knees and a very bad hip) and the weight of the little engine is just an embarrasing dunk waiting to happen, also as I am always single handed there would be no-one in the yacht to take the engine off me, so I don't even try.

 

[Seajet]

Cappen Boidseye,

I have found a huge difference in weight between 5-6 hp 2 & 4 strokes, I'm a reasonably fit 12.5 stone 53 yr old but while I find the 2-stroke easy to lift, the 4-stroke is a real problem.

Through sheer incompetence on my part I've managed to submerge my Mariner 2hp 2-stroke tender engine 3 times over the years, but apart from new crank bearings ( easily done ) it's shrugged it off.

As for Seagull engines, I agree, the spawn of the devil and best polished, hung on a pub wall !

 

[VicS]

Having seen a lot of folk on this thread slagging 4 strokes, I have a four year ols Suzuki 2.5 hp for my tender.

. Maybe modern 4 strokes are heavy, it isn't as heavy as my old seagulls were, also it starts when I want it to, which is nice!

Your Suzuki DF2.5 weighs 13.5kg according to the specs

My Seagull 40+ weighs ...............13.52kg ... I know that 'cos I just weighed it! Not a significant differenece.


I actually use a 40 Featherweight, which is marginally lighter but a lower power of course, on my tender. It always starts without difficulty. In fact have started it without the cord by spinning the flywheel between my hands!

Both date from the early 1970's have been converted to run on 25:1 fuel mix and are in almost as good as new condition. They will see me out without doubt probably outlast Seajets' pub wall too.