unbiased 2 V 4 stroke test

[Noelm]

Kind of longish, but may be mildly interesting to some, on the weekend I had the pleasure to fish from two almost indentical Boats, but one with a pair of "new" technology 2 strokes and an almost indentical HP twin 4 strokes, now, no brands or models, I don't own either Boat or brand so I am not bashing or praising either, this is just an observation, so here goes.... both types of Motors started almost instantly first thing in the Morning (expected I guess), the 2 strokes are noticably faster/punchier, we spent a fair bit of time trolling, and here the 4 strokes are a much better package, much quieter at about 1,500 to 2,000 RPM, but above about 3,500 both Motors sound about the same (believe it or not) next comes the smell factor, now let me tell you, they both burn Petrol, so they both have fumes, but the 2 strokes did smell different, no doubt about it, at troll the mix is about 120:1 or less, so there is no smoke, BUT definately a different smell, now to cruise, the 4 strokes are by far the best in this area, no doubt about it, I think the problem lies with the 2 strokes distinct "power band" in a following sea, the 2 strokes will bog down quite easily, and need a handful of throttle to get going again, whereas the 4 strokes have a much flatter "top" on the torgue curve and a drop of 500 RPM does not seem to affect the power to maintain a constant speed so much, where the 2 strokes, a drop of about 500 RPM sees you floundering (almost) now both Boats where launched together and retrieved at the same time and both filled before the weekend and at the end, the 2 strokes used about 18 litres less, now this could be for a number of reasons, one Boat might not have been filled to the "tippy top" first off, the filler might have cut off before it was completely full, who knows? as I said this is just observation, not scientific, so in overview, I guess the 4 strokes provide a slightly better "package" when trolling and long distance cruising, but there is really bugger all in it, and fuel usage is practically the same for both operating principals, so there you go, as much as possible, a truely unbiased look first hand to compare the two "players" in the Marine Motor field.

[STUIE63]

Noel how much fuel was used this will make a difference with the comparison as if only 50 litres was used then 18 litres is a big difference but if 200 litres was used then the difference is a lot less
Stuie

[Noelm]

from memory it was around 180 litres, so the difference was almost nothing, BUT as mentioned, it would depend on how "full" they where before we started out, there was no real accurate way to assure this, and no fuel use metres were used, so it is only a maybe perhaps!!!

[STUIE63]

Thanks mate
Stuie

[Outsider1]

Thanks for the first hand real life observations there Noelm, much more value than more common hearsay or innuendo that gets posted. What size motors were they?

I am interested particularly in the cruise and following sea observations. Smithy has made very similar observations of 2 stroke DI motors in other threads . I certainly can relate to it as being a characteristic of my old carby 2 stroke, but so far it has not shown as a trait for my new 2 stroke DI?, perhaps I have not been in bad enough conditions to bog it down yet.

Cheers

Dave

[Getout]

Thanks Noelm. Its nice to read a non-biased offering occasionally.
Were they the same HP rating?

[Noelm]

both 150HP, in my own Boat with twin 115 Evinrude Fichts, they have a very definate Power Band, you drop below that and you need some throttle adjustment to get back again, then ease back again to stop you from taking off, seems to be a "feature" of high performance 2 strokes, if the Sea is calm or really rough, it does not matter too much, but if you are cruising and need to "go uphill" then you really notice it, mine are positively gutless getting on the plane, but once there you need to be awake or you will be going way too fast, but running in their "happy zone" they are faultless and at Troll there is no fouling or farting around, so I guess untill I get another Boat (soon) I just live with it and have accepted it aver the years, now it is just normal for me.

[ozbee]

sorry to dis agree noelm i cant in any conditions be able to actually bog my motor down 500 revs in my 250 di patriot whether i punch guts into a wave, flog it full lock , in fact its quite boring its power band seems to be from wow to go . i think you could be comparing the affects of different prop pitches as in my case i can load 8 people in plus 350 litres of fuel and make very little difference to top end in fact from crawl to flat out theres hardly a difference of .02l/nm a sure sign of a direct injection engine meaning its powerband is pretty well depended on how much pressure the fuel is delivered. problems start to occur when you try to run low cc engines instead of ho engines perfect example is is the packages of two 150 etec on 680 patriot, you haven't got a hope in hell without changing props of getting up on one motor yet a 200 ho it would jump out all on its own and fly.with ho engines you can run a lot larger square pitch prop giving more freedom of load and speed factors for varying conditions.does it really matter not a lot i would say as technology changes we are more likely to see a emergence of direct injection into fourstrokes probably with a synethic oil injection on top of sump so as to be able to run far leaner mixtures delivering figures of over 40% better fuel economy over the four stroke motor of today.There is already over a million engines running today but unless you have the dollars eg alfia remo it will be a while yet.

[finding_time]

, now to cruise, the 4 strokes are by far the best in this area, no doubt about it, I think the problem lies with the 2 strokes distinct "power band" in a following sea, the 2 strokes will bog down quite easily, and need a handful of throttle to get going again, whereas the 4 strokes have a much flatter "top" on the torgue curve and a drop of 500 RPM does not seem to affect the power to maintain a constant speed so much, where the 2 strokes, a drop of about 500 RPM sees you floundering (almost).


Good report Noel! The above is why i ( Personally) like 4's And as i , smithy and many others have said fitting a 4 to a boat can make it a real pleasure to drive offshore. We do a lot of km's though and 2+hour straight runs are common but if you were just doing short trips i'm sure some would enjoy more hull shot . I know my mates 685cc was transformed as a offshore boat by getting rid of the di 2 and fitting a 4 stroke!

Ian

[Homer_Jay]

Good to hear what seems a very UNbiased opinion of the two.

Just goes to show I think, that the both have their faults and benifits.... both are great motors but it just depends on what your doing.....

Some will prefer 2stroke and some 4 stroke.
Neither is a BAD choice!!

[tin can marlin]

Hi guys it is good to see someone not telling us what brands they were. Well done noelm it is a credit to you how you have handled this.