TWO Vs FOUR STROKE ENGINES

[Manos]

Dear All,

I have been talking to many sea people about the benefits of a 2-stroke engine Vs a 4-stroke motor.
However, many (and I mean MANY) are keen to purchase a 4-stroke, which is heavier, slower and MUCH MORE expenssive than a 2-stroke motor.
Do you think that it may worth our while to have a debate on this subject??
or it has already been discussed??

Is just a thought.

[Julian]

Manos

Morning. I think we have been through this topic recently. My own opinion is that a 4stroke engine is better than 2 stroke engine especially with the huge savings on Fuel and Oil. I know the engine is heavy but extra weight on a Rib is not allways a bad thing as long as its balanced out.

Julian

[Keith Hart]

Depends on the size (take note Matt). If, like me you have a small one (engine, engine you fools), and have to carry it, then a 2s is far better because they are about 40% lighter. Anyway my little one is so economical that the cost of fuel is not an issue.

BTW there is an interesting article in the Oct RI magazine comparing diesels and four stroke engines. So go out and but RI and read it. (He's managed to get another ruddy plug in for that damned magazine again)

Keith (I can lift mine up, can you) Hart

[Manos]

As I said I wasn't sure whethere this topic was discussed in detail or not so. MY APPOLOGIES !!
However just to say a few words on your comments if I may.
I am of the opinion that that extra weight on the back is not necessarily as advantageous as if you say had extra weight in the middle of the boat?? (balancing etc)
I have also heard that 4-stroke engines (agree with you that they are more economical than 2-stroke) are a pain to service.
Say, you cannot do an oil change by your self but you need to take it to a dealer.
In some instances the engine has to come off the transom to change the oil.
Also they are not time tested for reliabailit enough.

Any way if this subject has been dioscuused better drop it then unless any one else wants to contribute.

[Manos]

Nice one.
Well (you started it fisrt) if yours is so small ..... I bet it doesn't need any help to get up (must be permanenetly standing) and also should consume less. Don't worry though Keith from what I heard lately size doesn't matter

FYI mine however, is toooooo big and needs some assistance and support and it also consuuumes toooo much (fuel I mean)

Seriously though for small engines , as you said, 2-stroke should be the engine type (I think).
However, from what I know in Switzerland for example in the lakes they do not allow 2-stroke engines any more (big or small). Is it the same in the UK?? or the law hasn't arrived here yet for implementation??

[Alex Brown]

The newer 4-stroke engines now are getting lighter it seems.....

Take the Suzuki 4-stroke 140hp engine for example (which I have just ordered), that engine is I think 180kg, whilst an Optimax 150 is in excess of 200kg.

It is only going to be a matter of time before the lower hp 4 strokes become matched for weight (almost) as the 2's.

There are still arguments for the hpdi (and equiv) 2 stroke engines too, and everyone has a different opinion on what's best

-Alex

[Andy]

Should you not also be looking at 2 stroke HPDI engines and comparing those to 4-stroke. These give 2-stroke performance and weight savings but are far more efficient on fuel, nearing if not matching that of a 4-stroke. They are also quiet ....

If this is true about HPDI engines (I have not bought mine yet so I have no practical experience) then why bother with a 4-stoke at all ....?

Anybody able to clarify.

[narked]

Ta for that Keith,
Even though I have next to no knowledge about outboards, I had gathered that a 2 stroke would be a better option for when I get my SIB, mainly due to the weight issue.

Matt

[Richard B]

Also for SIBs it's a good idea to have a 2-stroke as they will survive being turned upside down, where a 4-stroke needs to be kept the right way up so the sump doesn't loose all the oil through the crank-case breather. Fuel consumption's not an issue for little engines as there's only so much a 250cc engine can get through!

[Simon Guest]

On larger 4 stroke versus modern 2 stroke (Optimax, Ficht RAM, HPDI), this has indeed been discussed before, for instance here
http://rib.net/forum/showthread.php?...ol+consumption

... but I didn't see any conclusion to the discussions.

(Like: how do the running costs compare? How do the noise levels compare?)

cheers,
Simon

[Manos]

Gota an idea

For the benefit of all
I have a Greek RIB Mag (FOUSKOTO SPECIAL EDITION 2002) with tests of 4 and 2 strokes engines. I will try to translate the most important points and will post atable with test results during the wekend.
If Michael The Bat has another of these mags i.e THALASSA ets please let me know so that we can do it together.

[DJL]

This is a slighly scary debate for me to read. I have just decided to sell my 60HP Merc 2-stroke and change it to the 60HP Merc 4-stroke. The change is mainly down to the events that unfolded on the Weymouth cruise.

The weight difference between the 2 and 4 stroke is only 12kg, 12% heavier. The new EFI 4/s are supposed to be alittle more sportier than the carb versions. Although who knows, whatever engine you buy, the sales man will tell you its the best around! You can also use the SmartCraft gauges with the new EFI engines.

Will be able to give direct comparisons between the two engines in a couple of weeks. Just hope performance doesn't drop too much.

We had a 4-stroke 9.9hp Yamaha on a river boat on the Thames for a couple of years. It was so reliable, started first time everytime, ran 3/4 throttle for about 7hrs a day for weeks at a time. Servicing was easy, the boat came out each year for an antifoul. Took about 30mins to change all the gearbox/sump oil, fuel and oil filters filters, spark plugs etc.

Daniel

[Keith Hart]

Pepper

How true, I almost forgot. Yes, if you are humping the engine about and laying it down in the back of the car then a 2s is a must. Before you take the engine off MATT, disconnect the fuel line and let the carb empty out. Then you can lay it down no problemo.

Keith (two strokes are all it takes!) Hart

[Richard B]

Originally posted by DJL
...down to the events that unfolded on the Weymouth cruise...

Daniel - what event(s) in particular convinced you to change to a four-stroke engine? What's the link between your fine display of boat handling in a storm and a change to your propulsion technology? (Sorry if I'm embarrasing you again!)

Anyway, I'm trying to budget for a RIB next year, but It'll have to have a 2-stroke engine as I won't be able to afford a 4-stroke engine It looks to me like the break even point (in terms of fuel consumption against capital cost) comes after several thousand miles.

[batfalcon]

I ' ve got somewhere a test of a FICHT Evinrude 150 vs a 2 stroke Evinrude I think, ( or something similar) but I really don't think that it covers the theme of the current forum. Anyway it's yours if you want it.

Personally I prefer the ease of service of a 2 stroke, the smell of the burning oil & fuel of a 2 stroke and the silent power of an electric motor which unfortunately isn't present on the hi tec scene yet.

(The hi-tec do-it yourself maniac)

[JCW]

Daniel,

I have owned both the 4 stroke 60HP Mariner non EFI and EFI. I currenly have the 60EFI and have used it for around 100 hours this season.

I find the EFI very good, 20% more economical than carbed variant. It has slightly more torque than the carbed engine too.
A big plus for the EFI is stable tick over, smooth power delivery and always first time starts even when cold or if the motor has not been used for a while.

I can not comment on the 60HP 2 stroke, however my Rib set up is more economical than when I used to run a 15HP 2 stroke Mercury on a 3.4m Zodiac fastroller!!

[DJL]

JCW, its nice to hear you are happy with it. It sounds like the EFI makes quite a difference.

Pepper,

Going back to Christchurch on Sunday we averaged about 13kts, which works out at about 3200rpm. Even at these engine speeds we were drinking a large amount of fuel. 4/s are much more efficient at lower speeds and I think I would have saved alot of fuel. The 9.9HP I had on the Thames used 2/3 less fuel running at 1/2 throttle rather than 3/4. Also I like the idea of having more power/torque at the lower speeds in rough weather.

The main reason though is that I need to put an A-frame on my RIB, and I can't fit one with my aux engine (Need a bigger boat ). So I decided I would sell tthe aux and basically I have been offered a new 60HP fourstroke EFI for my 2/ and my 4hp aux.

The aux was starting to be a pain anyway, after getting back to Christchurch on Sunday I was going to use the aux to go up river, but it had jammed itself up which would have been great in an emergency. Took an hour to unjam it!

edit: I may sound silly but that Weymouth trip highlighted all the c**p things about my boat. Even things like having the GPS/Echo sounder on the same fuse at the Nav lights.

[Manos]

I saw that you are interested in purchasing a RIB next year without wanting to be pushy may I suggest that you have a look @ our site (address @ the bottom of this message) and we may be able to assit you on that. Or even email me @ falcon.international@talk21.com specifying your requirements.
Our package prices are really LOW and include trailer, boat cover, engine VHF, GPS and of course engine of your choice etc etc. Delievry time from ordering max 4 months.
Further, the quality of the FALCON RIBs is excellent.

[Manos]

As I said at the begining of this thread I am now posting tables with some of the motors 2 and 4 strokes that I thinkmay be of interest to the Forum

EVINRUDE FICHT RAM 115 (90,75) – 2-stroke
Dim 91x66mm
2 stroke, water cooled, V 600, 1726 cc
BHP 115 @ 5500 revs or
Direct injection Ficht, oil lub injectors
Reduction ratio 2.25:1 or 2.00:1
Alternator 35A
Weight 166 kgs
Axle L 635 mm, S 508 mm

EVINRUDE FICHT RAM 3.3 ltr V-6 900 , 3300 cc 2-sroke
Note: The block of 3300 cc is the same for 200bhp, 225bhp and
250. The only change is the performance due to modified CPU, weight,
transmission and revs 5750 remain the same for the three different
bhp outputs
Dim 98x73 mm
BHP 250- @ 5750 on the prop axle
Direct injection FICHT RAM (Sagem)
Reduction ratio 14:26
Alternator 35A (2 bat charging system)
Weight L 234 kgs, XL 236 kgs

HONDA BF 200/225 4-stroke @ 5500 revs, 3417 cc, water cooled, V-6 600 , 24 valves, 1 cam shaft (x2) and VTEC system (BF225), 3471 cc
Dim 89x93
Electronic injection with O2 sensor, variable, two stage, air intake
Ignition digital
Reduction ratio 1.87:1
Props up to 15 ¼ in diameter
Power trim from –40 to +160
Power tilt 720
Alternator 60A (48A @ 1000 revs and 60A @ 2000+ revs)
Total length/width 920mm/625mm
Height LD 508/mm, XD 1800mm, XXD 762mm
Weight LD 267kgs, XD 272 kgs, and XXD 277 kgs

MERCURY 115 4T @ 5500, 1741 cc, 4 straight cylinders, water cooled, with 2 cam shafts and 16 valves
Dim 79x89
Electronic injection
Ignition electronic with automatic timing
Alternator 25A
Reduction Ratio 2.07:1
Transom Height L 508mm/SALTWATER 635mm
Weight L 175kgs/SALTWATER 184kgs
Prop Pitch 9” to 26” (10” to 23” SALTATER)

SUZUKI DF 90 BHP and 115 DF @ 5500 revs, 4STROKE, 4 cylinders, water cooled, 16 valves, 2 cam shaft and OFFSET Transmition axle (Hydraulic belt tensioner), 1950 cc
Dim 84x88 mm
Electronic multiple injection system
Digital ignition with EFI total management system
Alternator 12V 40A
Reduction ratio 2.59:1
Prop Pitch 17” to 23”
Weight L189kgs/UL 194kgs


YAMAHA F 60BHP @ 5500 revs A 2002, 4STROKE, 4 cylinders, 8 valves, 1 cam shaft, 996cc
Dim 65x75
4 carbs with acceleration pumps
CDI computer monitored ignition
Reduction 1.84:1 (13:24)
Alternator 12V 10A
Power trim turn 800 (400 +400)
Transom Height L 508mm
Weight 113 kgs

YAMAHA F 100 BHP @ 5500 revs, 4STROKE, 4 cylinders, 12 valves, 2 cam shafts, 1596cc
Dim 79x89
4 carbs
CDI microcomputer monitored ignition
Reduction 13:30 (2.30:1)
Alternator 20A (12A @ 1000 revs)
Exhaust via prop
Single bottle power trim
Weight L 164kgs/XL 167kgs

YAMAHA F 115 all same as F100 except
1741cc 100 bhp @ 5500 revs
Electronic digital ignition
Electronic injection system EFI
Alternator 18A @ 1000 revs – 25A @ 6000 revs
Reduction 13:28 (2.15:1)
Weight L 185kgs/XL 189.5kgs (counter rotating available)

YAMAHA F 200/225 BHP @ 5500 revs, 4STROKE, V-6 600, 3352cc
Dim 94 x 8.5 mm
Electronic injection MPI
TCI transistor ignition system
Prime start motor
Alternator 32A @ 1000 revs and 45A from 2000 revs
Reduction 2.00:1 (15:30)
Weight 272kgs

YAMAHA 200 BHP HPDI @ 5500 revs, 2STROKE, V6 760, 2596cc
Dim 90x68
TCI controlled by CPU ignition
HPDI, direct injection system, with 6 injectors and high pressure pump (50 kg/cm2) belt driven
Alternator 45A @ 5500 revs
Reduction 1.86:1 (14:26)
Axles L 508mm/XL 635mm
Weight L 216 kgs/XL 222kgs

YAMAHA VMAX 200 BHP, 225 BHP @ 6000 revs, 2STROKE,V6 900, 2596 cc
Dim 90x68
CDI ignition system
3 twin carbs
Reduction 1.85:1
Weight 194
Long leg only

I also have tables with performace etc if any one is interested I can scan them and post them too.

Hope the above info can be of help.

[Tiger]

Part of the problem in choosing 2s v 4s is of course what are you going to use it for. (That old chessnut)

If you are going on long passeges running at higher speeds then there is not much in it on fuel economy, 4s being slightly better, but compared to HPDI you will struggle to tell I would say.

For tickover and low speed mixed with 100% power every so often then it has to be 4s. The 2s are very poor at low speed in comparison. I say this on the basis of safety boats that do a good deal of this slow speed work waiting for womething to happen. For a centre boat working at sea, the extra cost is recovered in fuel savings very quickly (at £1 / ltr its not hard)!

Other benifits of 4s are:
Fuel range is longer on average varying speeds (very important),
much less oil to buy / mix,
quiet.

In comparison the engine weight does matter but in triming the boat there many ways from where the spare can of fuel or anchor goes, to where you put your lunch!

As a last point, why oh why cant someone set a benchmark for fuel comsumption using the same base hull and change the engine (like the car figures). I think it is well beyond RI to twist manufacturers arms, but can't all the engine manufacturers say we use a make and model of RIB for this engine range for figures. eg 6.5m Tornado with A frame (close to standard fitout for many users) with engines between 100 and 225hp (guessing the plate)

It will never happen, but wouldn't it be nice to compare apples with apples, and not hear the dross from a salesman.

Tiger