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Old 06 May 2004, 15:29   #1
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two strokes four strokes

from what i can read from you guys ,it seems than four strokes for the same amount of hp are less efficient than two strokes in terms of fuel savings;what's the truth,is any body able to give me figures about that
i am concerned about the silence at iddle ,cause i am fishing with the engine on
4 stokes are probably less performant than 2 stokes cause of their weight

it sounds fo me than 4 strokes was easier and cheaper to maintain tue or not
thanks for all of that
i am looking at 150 HP
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Old 06 May 2004, 15:38   #2
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Roll on the debate!!

It is my understanding that for fishing with the engine idling at low revs and trolling around at low speed a 4stroke will behave better, and so may suit your needs. Not sure about this though!!

Their are plenty of threads already, on this but I think it all boils down to personal preference, and what you want the engine to do.
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Old 06 May 2004, 15:43   #3
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i am not trolling i am mainly concern about fuel economy
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Old 06 May 2004, 15:46   #4
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With the exception of the 90 and 130 honda fourstrokes an opti will use more fuel than a 4 stroke. It may not be much more but when the oil costs are added they are noticibly more expensive to run.

Have a look at suzuki 4 strokes, by far the best in my opinion at the 140 suzuki is quite a lot lighter than a 150 opti.
As for fishing, four strokes wont make the typical oily 2s troke smell at tickover and are quieter.
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Old 06 May 2004, 15:50   #5
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Very occasionally my optimax (2 stroke) cuts out if it has been running slowly for a longish period of time 1hr +. It does have 500+ hrs on it but apparently it has always done it, it is a 1999 model. This not really worrying as 1 –2 squeezes on the fuel bulb and it restarts first time and then runs very sweetly again.

Just passing this information on as a four stroke maybe better if idling for long periods of time.
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Old 06 May 2004, 15:50   #6
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Not sure that 4/ are easier to maintain than 2/ though...I think the mechanical 'simplicity' of 2/ makes them easier if anything. Having said that...I wouldn't have a scooby-doo with either of them. Checking the oil is a far as I've been!
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Old 06 May 2004, 16:15   #7
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preferences

Its down to what you want, in a boat invariably you are going to be in situations where you need extra or immediate umph,This is important towing toys, towing boats, making a rapid manouvre etc etc, four strokes will do this, but strokers love this sort of driving.Four strokes as we know have valves and cam chains, sump oil , and sump or four stroke oil filters. Two strokes dont have valves cams , oil filters.Two strokes having less moving parts can rev higher, their lubrication is with the fuel, as far as the cylinders are concerned. Four strokes tend to rev a little less, are quiter, and obviously reuse their lubricant in the cylinders with scrapper or oil rings removing it each time.
As far as power is concerned in a stroker its done in two cycles, but fours need to preform two more.Easily a two stroke will give you that immediate umph, more readily than its heavier four stroke counterpart with matched hp.I am not talking about dfi, two strokes as I know they can be heavy.
In reality I prefer two strokes, for lubrication, power cycling output, smell, sound , rev range , simplicity , ease of maintaince, and immediate umph on tap.
If I wasnt running a fast rib, but say a harbour launch, where I needed a quiter engine, not immediate umph relative to a two stroke, good fuel economy, and I didnt want to buy two stroke oil,
and never reved hard, I would fit a four stroke.
I just happen to be a fan of two stroke motors, but there are some amazing four strokes out ther, with plenty of power, up in the big Hp ranges, its down to choice and needs at the end of the day.
The boat and your needs and driving style should dictate the motor you use.There are benifits to both and down sides to both.
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Old 06 May 2004, 16:45   #8
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In our diving club we have 3 Yamaha 2 stroke engines & 1 Suzuki 4 stroke. We have a 30hp Yamaha premix on a 4.5m Zodiac, this has been the most reliable of the Yamaha engines it is also the oldest. We have another Yamaha 30hp auto lube on an Avon 5m & a Yamaha 40hp auto lube on an Avon 5.2m. These two auto lube engines have been nothing but trouble, the carbs have had to be stripped down & cleaned 3 or 4 times every year because of blocked slow running jets. All three of these boats & engines tend to use almost 2 tanks of fuel in a typical days diving.
Earlier this year we got a Humber Assault 5.5 with a Suzuki 70hp 4 stroke, this is a lot quieter and runs a lot better at tick over for long times, no smelly exhaust fumes & a typical days diving has yet to use 1 tank of fuel (yes they are the same size tanks)
I know 4 stroke engines are heavier, cost more to purchase & you have to change the oil & filter regularly but from my own experience I know what we will be getting in future.
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Old 06 May 2004, 17:50   #9
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9 months ago i was going to buy a diesel or 4-stroke RIB.

The reasons for discounting diesel are numerous, but those for choosing an Optimax over a 4-stroke may help you here, particularly because i was looking for a 150ish HP unit.

Firstly there was a poor choice of 4-strokes at this size. I don't like Suzuki's, that's just me - i know the new engines are supposed to be good but but i still don't like 'em.

The next choice i could find in 4stroke was a Yam 115 unit, which was similar in weight to a 150 opti

The 150 opti was several thousand pounds cheaper than the 4-stroke

I don't need to idle for long periods of time

I do like skiing and hence loads of low end power

The optimax smartcraft gauges are superb, really, really superb - do not overlook this.

I'm not trying to persuade you 2-stroke DFI is the route for you, if you are going to idle for long periods of time it probably is not. I can guarantee you non-DFI 2-stroke is NOT the route to go, consumption and resale are very poor. For info i will probably be replacing my sailing club's safety boat engines with 4-stroke units, although there are no DFI engines of the 40hp size available i would still choose 4-stroke here if there were.

With 70 hours and 1500nm under my belt I can confidently say i can acheive a little under 1nm per litre. If i open the throttle loads i can dent this figure. 1500 miles have used 7 tanks (1600li) of fuel.

I hope that is of some help!
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Old 06 May 2004, 18:02   #10
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Quote:
although there are no DFI engines of the 40hp size available i would still choose 4-stroke here if there were.
There's a new Evinrude e-tec 40hp. These are direct injection. Just thought I'd post this for anyone looking at the smaller engine sizes. Looks a good engine too. No run-in, First service after 3yrs. If they had Smartcraft and made em bigger than 90 I'd have gone for one.
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Old 06 May 2004, 18:06   #11
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Yamaha now have a 150HP fourstroke, only weighs about 20Kg more than 150HP opti-max.
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Old 06 May 2004, 18:18   #12
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Only 20Kg? Thats 10% more, and 5Kg less than a 225opti.

Anyone know the RRP? I reckon (guessing) £14k.

I'm not trying to dismiss 4-strokes, they have an application and it's nice to have a gap in the 4stroke market filled but i don't think you could put a 4-stroke 150 on a 6metre boat.
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Old 06 May 2004, 18:33   #13
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Most four strokes weight 10% more then equivalent 2 strokes. My 60 4/ weighs 11kg more than my old 2/ 60.

Yamaha 150 4 stroke costs 10k inc VAT. If I had the money i'd have one on the back of a 585 ribcraft/tornado.
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Old 06 May 2004, 20:36   #14
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For what it's worth, I was once told that 2s don't like extended tickover/low revs. something about varnishing of the cylinder bores. What I was told was that the petrol and oil mix sticks to the bore of the cylinder and makes an increadibly hard carbon/hydrocarbon layer that makes the compression drop because the gases/fuel air mix gets past the seal the piston rings make, stopping the engine and preventing startup. If this did happen the fix was to remove the spark plugs and squirt some oil into the piston (to increase compression), re-insert spark plug and when the engine fired give it WOT and this would burn off this varnish after a while.

I guess it makes some cense, but I'm yet to witness it myself so might be a load of twoddle, a quick call to an outboard service centre would probably tell you more though.

If it's true.........I guess 4 strokes then!

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Old 07 May 2004, 01:00   #15
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I can't believe that people on this thred are reccomending a 150 4 stroke over an Optimax 150. I bet they never owned and operated either!

If you are staying in a river or the throttle frightens you then get a 4 stroke. personally I don't buy a v6 to use on a river, If you want to make your spine tingle then get an Opti.

Most people that recomend Suzuki's haven't owned or used one, they just got turned on by the brochure and have one on order or not. So the opinion is not based on personal experience. (Alex B does have and use one)

Most people that recomend Opti's have em and are on the water a lot of the time. So they get used. Also I can't recall any Optiowner slagging them off.

At the end it comes down to power to weight. cost per horsepower and consumption. Optimax's are very frugal and anybody that says different is talking bollix. All engines are thirsty at full chat how does 77 litres per hour grab you from a new 4 stroke yamaha 225.




The only way I would consider buying a four stroke is if I was sponsored!
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Old 07 May 2004, 01:59   #16
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Rogue? I feel there may be a teensy-weensy bit of over reaction in your response! I have read over the posts in this thread several times and can only find one person recommending a Suzy (without owning one). Several people seem to be leaning towards Happymax.... I know that top Banana's outfit flies... quite literally.
Has a Suzy owner upset you recently? I've heard that they're all a bunch of smug bastards.... but if you want to upset them ask about fuel economy....77 litres per hour at full chat sounds quite good to me.. and I should know...
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Old 07 May 2004, 02:33   #17
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I'd be interested to know the WOT consumption of a big 4stroke. Of couse because few people except us Optimax owners are blessed with 'SmartCraft' i'm unlikely tyo find out. WOT see's 5200rpm with my current set-up and cunsumption is nearly 60lph, which i thought to be rather alarming.

Reading between the lines the Suk 4-s boys are getting worse consumption??? This of course is not a fair comparism, they are 250's and pushing a bigger boat. Anyone with a Sujuki 140 or even a Yam 115 ... any idea's?
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Old 07 May 2004, 02:35   #18
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Originally Posted by Jono
Rogue? I feel there may be a teensy-weensy bit of over reaction in your response! I have read over the posts in this thread several times and can only find one person recommending a Suzy (without owning one). Several people seem to be leaning towards Happymax.... I know that top Banana's outfit flies... quite literally.
Has a Suzy owner upset you recently? I've heard that they're all a bunch of smug bastards.... but if you want to upset them ask about fuel economy....77 litres per hour at full chat sounds quite good to me.. and I should know...


Hi Jono

I wouldn't describe you as smug!

nah nobody's upset me and I don't have a beef with Suzuki's per se. I just found over the last year that most advice for Suzuki's was derived from opinion rather than experience and in my world there ain't no substitute for experience. Most of the owners that were signing the praises were awiting delivery and I feel that an opinion on an engine has more creedence after the honeymoon period is over (say 100 hours)

I am aware of the OEM prices that Suzuki are offering and if I was making a rib wild horses wouldn't stop from supplying a Suzuli engine as the profit marging is lucrative. I imagine we'll be seeing more of em about soon so maybe at the end of next season I'll start paying attention to what people have to say about em


The prime motivator for the advice to go 4 stroke is fuel economy and I think that is a falacy and there is little difference between a high pressure two stroke and a four stroke in terms of consumption

what kind of figures are you getting or isn't it run in yet?

cheers
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Old 07 May 2004, 02:40   #19
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Originally Posted by Rogue Wave
Hi Jono
The prime motivator for the advice to go 4 stroke is fuel economy
I disagree, it's noise level and ability to tick over for long periods of time - add this to no requirment for oil and it's still an attractive option even if there is no consumption advantage.
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Old 07 May 2004, 03:09   #20
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Quote:
Originally Posted by Rogue Wave

The prime motivator for the advice to go 4 stroke is fuel economy and I think that is a falacy and there is little difference between a high pressure two stroke and a four stroke in terms of consumption

cheers
In a side by side test a honda 130 used the same amount of fuel as a Mariner 150 v6 2 stroke with a 10 knot les top speed which was a little scary. (Rogues Camel Rib and my Ribtec 6.5m) so I agree.

But I think the role of the rib should dictate what engine is best suited. The safety boat following wind surfers around a bay all day would suit a 4 stroke. The heavily loaded dive boat were weight is critical then 2 stoke injection for my money. Less clear is the 5.5 - 6m family rib used for cruising and fun. Perhaps there isn't an answer and its horse for courses.

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