Are 4 stroke engines that more fuel efficient than 2 stroke?

[saltystick]

When I went to a dealer, a big selling point was that my 90 hp Merc on my old bass boat was not as fuel efficient as the 4 stroke he showed me no matter the speed. As with most dealers, I take everything they say with a grain o' salt until I can ask around and do some research. No doubt they are quieter, but how much better at an average speed on 40 mph or less? (Of course I have to consider the difference in weight between my old Ranger and the aluminum fishing boat I've been considering.)

[Oldfart9999]

They are more fuel efficient, instead of firing every revolution they fire every other.
Rodney

[Sandman7925]

Much more fuel efficient. I think the only downside to a four stroke compared to a 2 is the weight.


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[FloridaFishinFool]

Yes. My 2 stroke uses nearly double the fuel of my old 2 star Yamaha 4 stroke

[D.W. Verts]

The new (now OLD) generation of DFI engines like my Mercury Optimax are very fuel efficient, especially when compared to the old technology 2S designs. The DFI's do not burn oil (they do use it, because they ARE two-strokes and it gets a little complicated...). Since they don't need oil in the fuel for lubrication, they can run a lot leaner.

I used to see 4-7 mpg with 225's using a SmartCraft fuel monitoring gauge.

I truly don't know how this compares to the modern 4S designs. I DO know that when I sold boats that (as an example) a 115 Opti would out-perform a 115 4S on a fishing boat or a pontoon, AND get better economy. The 2S doesn't work as hard, and is in the power band earlier.

But after being in jfly's new Skeeter with his 250 Yammy 4S, I'm a-thinkin' that maybe the rules have changed some. That is NOT the 4S motors I knew fifteen years ago!

[coldfront]

let's do the simple math

assumptions:
200 hp outboard @ $18000
20 gallon gas tank
$3/gallon gas


it would take 6,000 gallons of gas to equate to purchase price of outboard.  that's 300 tanks of gas.
so, over the life of the outboard, let's say you run 10 tanks of gas through the boat/year,

that works out roughly
4-stroke:  $3/gal x 5 tanks x 20 gallons = $300
2-stroke:  $3/gal x 10 tanks x 20 gallons = $600

thats a fuel savings of $300/year and would pay for a new engine in about 60 years.  but  you'd also need to factor in gas treatment, oil, etc.

the real number, though, is the cost differential between the 2 and 4.  that's where the real payback would be found

plus, buying now?  I'd go 4-stroke as  think that's where ndustry is headed.  2 strokes pricing might reflct this.

[Oldfart9999]

With more companies going 4 stroke only and probably most making nothing but 4 strokes by 2022 it becomes acadaminic as to price comparisons. The good news, at least Merc is dropping the weight of 4s and getting better hole shots with them.
Rodney

[saltystick]

....plus less pollution from unburned fuel with a 4s as compared to pre-DFI 2s motors. I can remember the clouds of smoke when guys started up their motors just before tx takeoff. This is going back at least 20 years. Still wonder if they added too much oil to the gas seeing as how I had far less initial smoke with my 90 Merc 2s which was made before DFI was mandated. But I did find this interesting:

from 25 to 300 horsepower a DFI two-stroke remains the lightest option at each horsepower rating. It is also usually less-expensive than a four-stroke. At low speeds, a DFI two-stroke typically produces lower exhaust emissions and better fuel economy than a four-stroke, a consideration for anglers that spend a lot of time trolling, or boat owners faced with long no-wake zones.

Boats.com

[Princeton_Man]

I've had no 4S experience of my own although I've read and been told by someone who I trust as an expert that Etec G2 matches and even beats the 4 strokes in fuel economy. Back in May Boat Test dot com did a comparison of the Etec 300 G2 and the Yamaha 300 four stroke on three different types of boats and while the difference wasn't huge, the Etec did have slightly better fuel economy.

When you're talking new motors here and now, I don't think there is a big difference in performance one way or the other. The 2 strokes are a little lighter, require less maintenance, and cost a bit less to maintain. The power band of a 2 stroke out the hole always puts a smile on my face but properly set up a 225 or 250 on a twenty foot boat will too. 

When I repowered a few years ago and replaced my Evinrude Intruder with a Etec G1, my fuel economy more than doubled and along with that cost savings I use a whole lot less oil. That G2 is supposed to be even more fuel and oil efficient!

[Oldfart9999]

I heard that even 'Rude will start making a 4s, rumor but what I heard or read.
Rodney

[FloridaFishinFool]

I believe you are right Rodney. I've been working the installation of the IBEX show in Tampa and some are already on show floor. I was allowed to photograph 2 of them.

I'll post them in an IBEX thread when I have some time.

IBEX is awesome! I'm getting first look and hands on all new boat products. I was allowed to photograph everything on show floor except the innovations awards new products.

So I visited them all. Yamaha showed me some of their new technology. The new 25hp is half the size of older yammies. They may look the same on the outside but not so on the inside.

[Princeton_Man]

I heard that even 'Rude will start making a 4s, rumor but what I heard or read.
Rodney

Yup, as hard as it is to believe, the G2 is nearing the end.