2 Stroke or 4 stroke ? exp comments please

[Madai]

I am undecided about which engine is best for my project

5.4M almin Tinny, high sided centre consol.

I have been told that 4 strokes are approx 30% more efficient fuel and obviously quieter.
What about power and prop thrust ?
Would a 70HP Evinrude 2 stroke be equiverlent to a 50HP 4 stroke ? How does it work regarding the two types ? OR Is it 70 HP to a 70 HP ??
Can someone please give me the specs of comparing the 2 stroke to a 4 stroke please.

Cheers
Madai

[Rainbowrunner]

if you can afford it go the four stroke.
The 4s are way powerful and responsive enough not to have to worry about the difference, imo.

I only bought a 2st because of price.

[krazyfisher]

just my thoughts

2/s- more power, cheaper, use more fuel, noisey

4/s- less power, dearer, less fuel, quite

injected 2/s- even more power, as dear as 4/s, as good as 4/s on fuel, not as quite as 4/s

all will do the job

[Spaniard_King]

Madai,

A 70 hp is a 70hp!

2 stroke Definately cheaper, uses 2 stoke oil, smokes, noisey. Light

4 stroke Quiet, no smoke, no oil mixing, 70% more fuel efficient at idle and more fuel efficient through the rpm range, heavier than 2 stroke. Will perform just as good power wise if proped correctly, Will last twice as long as 2stroke before rebuild required. Tend to be more reliable than 2 strokes. Higher servicing costs. Better resale than 2 strokes

In suming up what you save on the purchase price on a 2 stroke you will put back into it in fuel costs and you will loose out on resale with a 2 stroke.

If you bought one of each and kept them for 1500hrs I recon they would end up being prety close on total cost factoring in all fuel, maintanence and resale value, I guess the overiding factor is purchase price, get over that and a 4 stroke will be a much more rewarding engine to own
cheers

Garry

[Hagar]

Madai

I have just changed over from a two stroke 115 to a four stroke 115 although on a different hull .

My observations . The four is quieter at idle and there is no smoke fumes at all - big bonus trolling . At mid to high power the noise factor is less but not greatly . Uses way less fuel . Is definately heavier on the back of the boat and this is noticeable sometimes at low speed . Basically as Gary says I prefer the four stroke . I had to go four stroke as there is no 115 E-tec injected two stroke yet but I would have given this serious consideration if it was in the marketplace .

Chris

[Bert007]

Two Strokes are now being wound back in production all over the world. there are places in the US that do not allow the use of them.( same with Motorcycles. try and buy a two stroke road bike thats not some glorified scooter. )Keeping the oceans cleaner I guess is the reason behind this. Cheers, Bert

[billfisher]

Bert 007,

The US has a lot of large freshwater lakes that are used for drinking water. This is the reason that 2 strokes are banned in some locations. I don't think they are ever going to be phased out. Perhaps 4 strokes will fall by the wayside eventually with the advances in 2 stroke technology.

As to the original post I think basic two strokes are the best choice for the average boater doing 50 - 100 hrs a year. On motors 90 hp and under you are not going to save all that much on fuel, especially if you don't do a lot of trolling. Remember that at cruising speed (4000 rpm), 2 strokes don't use much more fuel. The small saving is offset by the higher service costs and the fact that they cost nearly twice as much as the equivalent 2 stroke. Also they don't have the same punch and acceleration as 2 strokes and this coupled with the extra weight can detract from the performance of small boats.

As to the longevity I haven't heard much about the 4 strokes as they haven't been on the market that long. I have heard that a rebuild is much more expensive though, making them a throw away item. For resale price you will get more for 4s only because they cost more new. As a % I don't think they retain more value than a 2s.

[FNQCairns]

The marketing of 4st motors always relate their fuel savings and quietness to conventional 2st carb engines and fair enough. Although they never relate prop thrust and torque in the same manor.

4st are slugs Hp for Hp some even use an extra set of gears in an attempt to make the package work so that a decent diameter propeller can be run.

They are 'on the water' a compromise, a person can make them snappy in response like a 2 st but they will be at WOT while the same hp 2st is at cruise! a person can make them cruise at an acceptable RPM but they will respond elsewhere like they are towing a trailer.

Along with the 30ish % fuel saving comes a 30ish % decrease in real usable power, 4 st have been around for around 40 years as water cooled outboards we probably will not see a great improvement in power in the near future if reliability and consumer cost effectiveness are benchmarks. A 70hp 4st makes 70hp only in the last 5% of it's rpm range same with a 2st - how much useable hp does each type make at half throttle!!!!! ;)

If someone has a 115hp conventional 2 st and re-powers with a 115hp 4st it will 'go' like a an 80 or 90hp 2st as yet that cannot be avoided, #consider also in this scenario the real world fuel savings are shaved somewhat.

Madai the next modern engine I settle for will be a 4st but it will be 20 to 30% larger in HP than if I was buying a (any) 2st.


cheers fnq

[vertico]

my 90 etec goes like the clappers, uses bugger all fuel and bugger all oil.
dont have to service it in the first 300hrs and havent had a drama yet.
There is no 2 stroke smell to it at all and it is nearly as quiet as a banger.

[Sportfish_5]

Once you go 4 stroke you will never go back ;)

The newer ones from Suzi(140 to 175), Honda (135/150) and Yammie (150) are right up there with the smart 2 strokes for p/w ratio and holeshoot (although I dont know why everyone gets hung up on that chestnut unless you ski or race boats). My boat is a fishing boat and the holeshoot wont get me in trouble crossing costal bars 4 sure.

The 30% fuel saving is another beauty that is quoted by everyone. That figure is calculated on a certain boat in certain conditions in a time "snapshot". Real boating time for my type of fishing in my local conditions would have that figure closer to 50% or even more. I know in my case that repowering from a 115 yammie carb 2stk to a DF140 Suzi has reduced fuel on same trip for the way I fish is over 50%.

Service costs are service costs no matter what unless you do it yourself or not at all ::) Time will tell on the 300hr ETEC interval and it sounds really good while it is in warranty but I would still be checking it over once per year for piece of mind after the warranty was up.

Your choice should be made for your circumstances - if you you dont really use it much and do 50-100 hrs/yr then save the $$ and buy 2 stroke carbie. If you travel long distances offshore and troll heaps then you will need to really look hard at the 4 stroke/high tech 2 st engines. Dont get hung up about resale value of 2 v 4 as you will never get sleep worrying about that issue.


Best of luck with your decision


Greg

[billfisher]

Sportfish 5,

Do you do a lot of trolling? I think with my useage (which is not untypical), the difference would be less than 30%. I usually head out at 20 - 25 knots and fish at anchor or by drifting. I have seen the fuel consumption figures for the Yammaha 100 hp 4 stroke at around 15l per hour at cruising speed. I get similar figures with my 13 yr old Tohatsu 90 hp 2 stroke. When I (rarely) do a few hours of trolling the fuel consumption is much worst than a 4 stroke. However when I troll I usually have two others on board and we share the costs.

[Sportfish_5]

Billfisher - yep for the majority of the year it is lots of trolling and thats why my usage has halved. The yammie was very very thirsty when trolling between 6-12 knots. I dont worry too much about the litres / hour economy anymore as I dont have a fuel flow meter yet. What matters to me is how much it costs me to have a day out doing what I like to do.

Not having a go at you about the 30% comment as I have read it elsewhere as well and it seems to be the "benchmark figure" quoted but in my experience it is more than that for a total day out fishing. Like I said - you need to look at just what you want to do with your boat - how many hours, what style of fishing to make the call on 4/hi tech 2 v traditional carbie 2 st


Cheers

Greg