Fuel useage good or bad for a 2 stroke.

PJ72
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Re: Fuel useage good or bad for a 2 stroke.

Postby PJ72 » Mon Jun 11, 2018 11:58 pm

Just my 2cents about the use of premium or regular fuels.
Most boat fuel tanks are vented, so fuel breathes more than in a car, (cars tanks are sealed to reduce emissions)
So fuel will go off quicker in a boat that in a car, my recommendation would be if you use 91 octane fuel, use an additive to help the fuel retain that octane rating, You can also use a higher rated fuel (95 octane) with an additive to make the fuel last longer again, as it's the lack of the volatile chemicals and low octane that cause running issues
As fuel ages, it loses the most volatile chemicals first, which lowers the octane rating of the fuel, and starts to cause running issues including increased consumption, after that, the fuel starts to seperate, and leaves a gum residue in your tank and fuel system, this causes problems with filters, pumps, carby's/injectors etc.
In my experience, my fuel bill is the smallest cost of owning a boat, I use an additive over winter, and only use 95octane fuel in my boat, car, my lawnmower and wiper snipper (my mower and wiper snipper are 19 years old). For the sake of an extra 10-15 cents per litre I have peace of mind and they seem to run better, (smother idle and acceleration)
From what I've been told, premium fuels take a lot longer to get to the separation point and start gumming up your fuel system
I used to have a Ford Fairmont that I put on gas, I used gas most of the time and went through a tank of petrol every 3 to 4 weeks, I started have problems with running on petrol, rough idle, stalling, no power. Then the fuel pump died. I removed the fuel pump and it was covered in a dark brown gum, I ended up having to replace the tank, fuel pump and filter.Then I had to remove and clean the injectors, fuel rail ect. That's when I started looking for info on fuels



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Lightningx
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Re: Fuel useage good or bad for a 2 stroke.

Postby Lightningx » Tue Jun 12, 2018 12:15 am

Well said :thumbsup:

phil1818
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Re: Fuel useage good or bad for a 2 stroke.

Postby phil1818 » Tue Jun 12, 2018 6:39 am

80-100km more from a tank using premium that’s gold :rofl:

smile0784
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Re: Fuel useage good or bad for a 2 stroke.

Postby smile0784 » Tue Jun 12, 2018 7:16 am

blacklab99 wrote:Hard to make a call without knowing what the hull is,
If an old 2 stroke like that is pushing a heavyish 5.5 mtr fibreglass with a deep V, 1ltr per km could be right, but your result is worse than that.
Hey, a good proper service always helps, but those old johnsons are getting long in the tooth if it is a 2003 model,
But again, whats it pushing ????
The new er 2 stroke efi's get some pretty reasonable numbers, but older ( under powered for the hull) carby versions, can fair suck the juice.
As mentioned, depends on what its pushing.....

Col

Its a5.6mt trailcraft

smile0784
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Re: Fuel useage good or bad for a 2 stroke.

Postby smile0784 » Tue Jun 12, 2018 7:21 am

purple5ive wrote:I've seen this whole premium vs non premium debate many times.

In cars ive noticed almost 100km more on a full tank between premium and non premium blends.
Even my outboards feels lot nicer to run when I fill with premium.
I can understand a big tank will cost a lot more between premium and non premium. But for a smaller totem tank its not going to cost a lot more..

Ricky.
I suggest you get it serviced properly first by someone who knows what tgey are doing.
Your leads could be shot for a start giving poor spark which in turn affects fuel consumption.. there could be a lot more or less issues.


The lead issue is probably my fault cos i checked the plugs a few weeks back must not put back on hard enough

smile0784
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Re: Fuel useage good or bad for a 2 stroke.

Postby smile0784 » Tue Jun 12, 2018 7:36 am

purple5ive wrote:I've seen this whole premium vs non premium debate many times.

In cars ive noticed almost 100km more on a full tank between premium and non premium blends.
Even my outboards feels lot nicer to run when I fill with premium.
I can understand a big tank will cost a lot more between premium and non premium. But for a smaller totem tank its not going to cost a lot more..

Ricky.
I suggest you get it serviced properly first by someone who knows what tgey are doing.
Your leads could be shot for a start giving poor spark which in turn affects fuel consumption.. there could be a lot more or less issues.


It was only serviced 4 lmonths ago by someone who mebt to be know what they doing and had sparks l, water filter, impella amd housing, oils checked etc fuel chcked for gunk but could find anything. Cant remember what else.



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smile0784
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Re: Fuel useage good or bad for a 2 stroke.

Postby smile0784 » Tue Jun 12, 2018 7:41 am

Just looked back over some pics and last time i was out was 3 months ago so fuel was getting a bit old

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ducky
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Re: Fuel useage good or bad for a 2 stroke.

Postby ducky » Tue Jun 12, 2018 7:58 am

FYI guys. Fuel companies are putting less “preservatives” in fuel these days. Gone are the days of 3 months shelf life. I believe they are making the move to reduce people’s ability to store bulk fuel. Whether terrorist related or not I don’t know.

As an aside. I did a quick google of my outboard and in the article where economy was tested it said not to use 98 as it can wash the bores more effectively than lower Ron fuel and can lead to dry bores over repeated usage. Who knew. I’ve religiously ran 91 in it but last rank put some 98 to see if it holds its life more over winter.

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Mattblack
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Re: Fuel useage good or bad for a 2 stroke.

Postby Mattblack » Tue Jun 12, 2018 8:24 am

I've been told the higher the ethanol (the cheap stuff), the longer the shelf life.
However, I've learn 2 things here...petrol goes off quicker in a ventilated boat tank & fuel companies are using less additives and fuels goes off quicker. (never used fuel stabliliser before, might be time to start)

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Re: Fuel useage good or bad for a 2 stroke.

Postby repspec » Tue Jun 12, 2018 10:26 am

5.6mtr trailcraft with a 115 johnson 2 stroke carby... pretty spot on for the fuel usage id suggest.

They are a carby engine that on a 5.6mtr boat, is underpowered (in my opinion 13yr marine mech) (it will be withing their recommended HP range, but its on the lower end id suggest). Also depends on the weight of the boat, how much gear you had, how many people, what sort of conditions you were in, how old the fuel was, quality of the fuel...i could keep going.

Most new fourstrokes are getting 1.5+km per litre. You have a 2 stroke carby, using 1-1.5ltrs per km...id be happy with that. If you are expecting more from it...you are going to be dissapopinted.
Easy soultion...fit a new motor to the max hp of the hull... ;)



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