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Thread: 2 stroke vs 4 stroke fuel economy question

  1. #1
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    Default 2 stroke vs 4 stroke fuel economy question

    Just a question on fuel economy 2 stroke vs. 4 stroke. If i have a 115
    2 stroke and upgrade to a 4 stroke and all else is equal how much better will my fuel economy be? I know thats a rough question but with the price of gas i am thinking about upgrading. I think its time any way but just wondering about fuel economy.

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    Assuming you're talking an old non-direct-injection 2-stroke, you should see roughly 30-40% improvement at crusing speed, and WAY more at idle speed. All out will be only slightly better.

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    What about direct injects. I've been seriously looking at a boat with twin 115 Evinrude Etecs. Its a very nice boat and, to be totally honest, I do like the Etecs. But I've been pretty well convinced that Yamaha 4-strokes are the way to go. So what do folks think about 4-stroke vs the modern 2-stroke in fuel economy...and if kgpcr doesn't mind....reliability.

    Hope this isn't a hijack.

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    Most new DI motors equal or exceed 4 strokes when comparing fuel consumption. But it doesnt make sense to dump your old motor just to get a new one with better fuel consumption.
    New motors are pretty pricey and it would take many years to see a payback in fuel savings for your investment. Of course, a lot depends on how many hours a year you are running the motor.
    Tennessee

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    Moderator Paul H's Avatar
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    Quote Originally Posted by Snowwolfe View Post
    Most new DI motors equal or exceed 4 strokes when comparing fuel consumption. But it doesnt make sense to dump your old motor just to get a new one with better fuel consumption.
    New motors are pretty pricey and it would take many years to see a payback in fuel savings for your investment. Of course, a lot depends on how many hours a year you are running the motor.
    Ditto's, you'll never save enough on fuel to justify the cost of a new 4-stroke. But if you're looking to extend your range, and perhaps add some more hp you might want to consider it. But with the 115-140's running $10k w/ controls, you can buy an aweful lot of gas!!!

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    Quote Originally Posted by Paul H View Post
    Ditto's, you'll never save enough on fuel to justify the cost of a new 4-stroke. But if you're looking to extend your range, and perhaps add some more hp you might want to consider it. But with the 115-140's running $10k w/ controls, you can buy an aweful lot of gas!!!
    DITTO AGAIN!
    I am running twin 2 stoke yammy 150's, same boat running twin 150 4 strokes, running side by side will burn only 1-3 gph less, *note this is a side by side on the water radio to radio test/ NOT scientific! no way to justify the 20/25K that will need to be spent on fuel issues only. BUT, when you start adding the unbelievable cost of 2 stroke oil to boot, dollars start adding up. I typically burn about 15-20 gallons of Amsoil each season, so there is another 450-600$. i figure with only 900 hrs on my motors that i can easily get a couple more years out of them, and am not going to get anything for them if i try to sell.
    As long as your motor is runninng good, run it! thats what I am going to do!

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    I have a 12yr old 90hp Merc. I want to get a 115 Yamaha 4 stroke. Just wondering if i will get better fuel economy.

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    Moderator Paul H's Avatar
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    Yes you should get better efficiency at cruise with the yammy, figure you'll be burning ~5 gph at 4000 rpm, depending on what boat you have and how it's propped, WOT will be ~10-11 gph. While you may be burning the same amount of fuel per hour WOT as the 90, you should also be going 2-4 mph faster, so your economy is better, but the biggest difference is at cruise, not WOT.

    One thing the think about is the yamm 115 is ~420#'s, your merc 90 is about 300#'s Depending on your hull, that extra 100+ #'s on the transom can really mess up your trim so you are likely going to have to do a fair bit of moving items around your boat to get it to trim out.

    Tohatsu makes a 90 horse direct inject 2-stroke that is very fuel efficient, and only weighs 300#'s, so might be a better option for your re-power.

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