Fuel useage good or bad for a 2 stroke.

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

Postby smile0784 » Mon Jun 11, 2018 7:44 pm

phil1818 wrote:Just trying to help I do know a fair bit about engines, built quiet a few that’s all


I didnt mean to offend just going but what a close friend told me thats all amd he seems to know a fair bit about boats and car and alike.

Im open to everyones opinion and like all the help i can get.



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blacklab99
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Re: Fuel useage good or bad for a 2 stroke.

Postby blacklab99 » Mon Jun 11, 2018 9:21 pm

What year is the motor ?
The hull type is going to play a major factor in your economy as well, including hull weight.
My 2005 125 merc 2 stroke, last of the carb models, at best I'd return 1 to 1.2 km per litre, hence the change to a 4 stroke.
Mate has same boat, with a 4 stroke on and gets 2- 2.5 km per litre.
Condition of motor etc etc , a lot of factors come into it, apples for apples outings etc.
But you should be at least getting 1-1.5 km per litres,
That result does sound a bit thirsty but.....

Col

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

Postby smile0784 » Mon Jun 11, 2018 9:32 pm

blacklab99 wrote:What year is the motor ?
The hull type is going to play a major factor in your economy as well, including hull weight.
My 2005 125 merc 2 stroke, last of the carb models, at best I'd return 1 to 1.2 km per litre, hence the change to a 4 stroke.
Mate has same boat, with a 4 stroke on and gets 2- 2.5 km per litre.
Condition of motor etc etc , a lot of factors come into it, apples for apples outings etc.
But you should be at least getting 1-1.5 km per litres,
That result does sound a bit thirsty but.....

Col

2003 or 2004 motor i think

blacklab99
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Re: Fuel useage good or bad for a 2 stroke.

Postby blacklab99 » Mon Jun 11, 2018 9:37 pm

Aussies 98 premium rates to U.S 92-93 Aki
We use different ratings for octane here, ours is in Rons there's is in aki,
So there premium is equivelent to about 92-93 in Ron standards.
no need to run premium in our outboards......
just my opinion.
All my classic British bikes however I run on Premium, due to possible pre ignition issues, they were designed for the old leaded fuel.
but boats, regular

col

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

Postby blacklab99 » Mon Jun 11, 2018 9:45 pm

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

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

Postby purple5ive » Mon Jun 11, 2018 9:48 pm

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.
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blacklab99
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Re: Fuel useage good or bad for a 2 stroke.

Postby blacklab99 » Mon Jun 11, 2018 10:19 pm

Yep, seen heaps of the octane debates,
Generally by people who don't understand the difference between the ratings and make ridiculous claims of eithers benifits.
Purple, I need to know the make of that car that does 100km more when using Premium ? I'll buy 2 Now !!

At best, an engine will run cooler on premium and effectively cleaner, hence, some motors sound better on premium,
It helps with pre detonation as it runs cooler, so better with some older engines.
A 2 stroke outboard with all that 2 stroke oil as long as its run regular, wont have any noticeable difference running on premium than 91.

The key is, run what the manufacturer recommends and don't let the fuel goes stale, fuel looses its octane level as it gets older, so more than 3 months old
its starting to loose octane.
So the upshot is, Use ya boat and get out fishing........

Col

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

Postby purple5ive » Mon Jun 11, 2018 10:32 pm

blacklab99 wrote:Yep, seen heaps of the octane debates,
Generally by people who don't understand the difference between the ratings and make ridiculous claims of eithers benifits.
Purple, I need to know the make of that car that does 100km more when using Premium ? I'll buy 2 Now !!

At best, an engine will run cooler on premium and effectively cleaner, hence, some motors sound better on premium,
It helps with pre detonation as it runs cooler, so better with some older engines.
A 2 stroke outboard with all that 2 stroke oil as long as its run regular, wont have any noticeable difference running on premium than 91.

The key is, run what the manufacturer recommends and don't let the fuel goes stale, fuel looses its octane level as it gets older, so more than 3 months old
its starting to loose octane.
So the upshot is, Use ya boat and get out fishing........

Col


all my cars ive had generally get me around 80-100km or more on start stop. not all the time but 80% of the time id say.

my 2 litre hyundai has given me almost double the kms on the way to sydney via the hume only using 98 optimax. ive had the car since brand new
now i understand its freeway driving and cruise control was used. but
when your constantly getting 100km more out of the same car by using 98 optimax vs normal 91shell then im not going to argue.
its the same with my subaru, 700km full tank on 98 and 650 or less on std 91. i know what im seeing as i reset my trip meter every fillup.
it was the same story with the soarer, the MR2 and Pulsar
They run so much smoother on the 98 stuff

the Outboard i have no way of saying because its a carby, only going off the way it idles and runs. no proof so to speak..
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Re: Fuel useage good or bad for a 2 stroke.

Postby cobby » Mon Jun 11, 2018 10:53 pm

First and easiest is dump all fuel from the tank into your cars and refill with fresh (20l). Even something as simple as a lawnmower uses more with semi stale fuel than fresh.
Take for a spin, have someone hanging over the rear checking the engine height when on the plane. Water should skim under the cav plate (the bigger one above the prop). If it goes over your motor is to low and the excess drag and strain will add in fuel use.
Check prop for bends, chips etc. as that also hinders economy.
Remove and replace spark plugs (less than $50 for the 4 of them).
Check exhaust when running for unburnt fuel. Get carbies checked and adjusted regardless as that will be the single biggest cause of crap economy out of the lot.

It should be using .8-1.6l per km when on the plane depending on your revs. I'd expect your current economy at 5.2k-wot not sitting at 3.8k

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

Postby blacklab99 » Mon Jun 11, 2018 11:04 pm

Ok, cant argue with what your saying,
Petrol suppliers say a "possible 5%" improvement in economy using premium, you seem to be blowing that out the window.
All of those cars you mentioned, manufacturers recommend 91...........
To many variables can exist, When I was a rep, doing near 10-12000km per month in various cars, I never had a noticeable difference.
Gone are the days with modern engines, if the fuel isn't left to go stale, does it really matter what octane you use.
Most modern out board manufacturers and indeed car makers are recommending 91, but if you choose, you can run higher.
I got into all this years ago, as mentioned before, for me with the engines I run and build, octane rating really matters with them, down to timing the engine suitably for the octane and with the type of internal running gear used. with modern VVTI engines, the octane ratings don't really worry them.
The people that are having huge issues are those up north, with the ethanol content in fuel, I suspect that in the future, that will be our only issue with fuel, which octane to use wont be an issue, it will all be about ethanol content, which some places and countries are already having huge issues with, we down here are quite lucky at the minute in that regard, long may it remain so.........

Col



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