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  1. #1
    Cadet
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    Jun 2012
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    perth
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    Default Why does my 1996 Mercury 115hp outboard use soooooo much fuel??

    First time boat owner... have taken my 18 foot baron out on the ocean... very smooth day... maybe 6km tops past Garden Island which is probably 12-14 miles from where we launched... we have used what I think is an incredible amount of fuel??? 60 -65 litres.... is this to be expected from a 1996 engine?? Averaged around 20 -25 knots cruising. Any ideas what could be causing this??? Any help will be appreciated.

  2. #2
    Lieutenant Junior Grade
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    Oct 2011
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    The Columbia Gorge, Oregon
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    Default Re: Why does my 1996 Mercury 115hp outboard use soooooo much fuel??

    Welcome to the world of boating. 15 gallons for 40 or so miles. Sound pretty good.

  3. #3
    Master Chief Petty Officer
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    Apr 2012
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    Default Re: Why does my 1996 Mercury 115hp outboard use soooooo much fuel??

    How's the compression on the motor. Lower compression = higher fuel consumption because the cylinders do not hold fuel as well as when the are fresh. These motors are roughly 50% efficient when running good. It's just the nature of the beast.

  4. #4
    Fleet Admiral Texasmark's Avatar
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    Default Re: Why does my 1996 Mercury 115hp outboard use soooooo much fuel??

    As I recall the numbers, some "Big Guns on here" like to use the numbers 10% of the engine HP rating at WOT in GPH consumption. So, at WOT a 115 would use 11.5 gallons per hour. Soooo based upon the above numbers, you ran at a reduced speed but for 2 hours and consumed 15 gallons; 7.5 gallons per hour. Sounds about right to me.

    Mark
    If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

  5. #5
    Master Chief Petty Officer
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    Default Re: Why does my 1996 Mercury 115hp outboard use soooooo much fuel??

    Quote Originally Posted by Texasmark View Post
    As I recall the numbers, some "Big Guns on here" like to use the numbers 10% of the engine HP rating at WOT in GPH consumption. So, at WOT a 115 would use 11.5 gallons per hour. Soooo based upon the above numbers, you ran at a reduced speed but for 2 hours and consumed 15 gallons; 7.5 gallons per hour. Sounds about right to me.

    Mark
    Agree and for an older motor like this, that's not too bad at all.

  6. #6
    Chief Petty Officer redjmp's Avatar
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    Mar 2005
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    Delta BC
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    521

    Default Re: Why does my 1996 Mercury 115hp outboard use soooooo much fuel??

    Expect 2 to 5 mpg on a boat.

  7. #7
    Lieutenant
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    Mar 2010
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    San Diego, CA
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    1,386

    Default Re: Why does my 1996 Mercury 115hp outboard use soooooo much fuel??

    I think your fuel consumption numbers are great for an "old" 2-stroke.

    (I put "old" in quotes because to me a motor isn't really old unless it's older than I am )

  8. #8
    Petty Officer 1st Class
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    Sep 2010
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    Australia, Tassie....East Coast
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    284

    Default Re: Why does my 1996 Mercury 115hp outboard use soooooo much fuel??

    depends too on how many POB you had,
    the baron is a fair size tub too,
    bit confused though...changing from K's to miles will do that..and l remember when we used imperial measurements,
    so you did around 27 k's one way and used 60-65 lts or did ~54 k's return on the same amount of fuel?

    my son has a 120 and will use that much pulling tubes and hooning around..

    of course, if you're in Sydney, the water is MUCH,MUCH harder to push through coz of all the "stuff" in it
    LOL
    happy little vegemite

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