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Fuel additives...anybody use them?


big Neil

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According to two Yamaha dealers I've spoken with there is 0 gain from using anything than the 91 recommended fuel in outboards specified to use that.

Back on track, I asked a good friend, who's a fuel and oil expert ( https://au.linkedin.com/in/sam-shatrov-49358328 ) whether he uses any additives with his outboard and no he doesn't, he simply puts in what the manufacturers recommend. His boat sits idle for months at a time, often only being used a handle of times per year.

Edited by JonD
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Here's the Mercury 200 EFI 2 stroke/ Mariner 15HP 4 Stroke - identical fuel guidelines ... min 87RON in US, min 90RON international. 

Ethanol mix not recommended.

IMG_1720.thumb.JPG.a4c9f321bc55b8151a0dc23c35fe4871.JPG

Both of my motors run from the same 250L tank.  The most I have ever used is 200L on one trip, the average bottom bashing trip has used 50L, the average trolling trip 100L, the average trip to Browns 150L.  So there is ALWAYS residual fuel left in the tank for months at a time. 

As per manufacturers recommendation, I can easily run on 91 Unleaded (ethanol free), but because of the residual fuel in the tank and the loss of octane due to sitting idle in a tank with a built in breather, the ONLY additive I use is 95 Unleaded (or 98 if its cheap).  It refreshes the total tank octane rating. 

Hey @JonD, I checked out Sam's linkedin profile... impressive. What's even more impressive he is also a Cabramatta lad of my vintage and I too started my professional life in the chemistry game as a Chemical Engineer! .... there must have been something going on in Cabramatta in the 80's that was chemistry oriented hahaha ! nuff said. 

Cheers

Zoran

 

 

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My wife called me away to help in the kitchen with the Friday night guests special dinner prep... so didn't have time to  say...

1. I always run with a water separating filter and change it every 12months

2. My motors will clock over 21yrs and 20yrs November this year (shit where does the time go!) ... so its a testament to their manufacturer ....and to how they are being treated - they must like what I am doing.

3. This discussion about fuel additives really needs to be viewed from several perspectives like - what the motor/fuel set up is and how its used.  Which is why we are getting so many opinions - we all know what we do that works for us !

Generally, if you run a smaller capacity fuel tank that you go through frequently, maybe 87 / 91 is great. If you don't use it but can shut off the tank vent to prevent evaporation of the volatiles (creating reduction in octane) then great. But iIf you have a bigger rig with lots of fuel sitting idle, with a breather vent, then as a minimum you may need to consider whats happening to that fuel and how to maintain the manufacturer recommended octane rating.

I won't go into the implication of how fuel is produced (cracking vs distillation) and the considerations around longevity - but lets just say that fuel is largely produced for the mass market being motor vehicles - where the average life span of the fuel in the tank is significantly shorter than what you see in fuel stored in large infrequently used boat tanks. 

Cheers Zoran

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4 hours ago, JonD said:

According to two Yamaha dealers I've spoken with there is 0 gain from using anything than the 91 recommended fuel in outboards specified to use that.

Back on track, I asked a good friend, who's a fuel and oil expert ( https://au.linkedin.com/in/sam-shatrov-49358328 ) whether he uses any additives with his outboard and no he doesn't, he simply puts in what the manufacturers recommend. His boat sits idle for months at a time, often only being used a handle of times per year.

Yes Sam moved down here on the south coast about the same time as us, our kids have all grown up together. He's a great go to for any oil info.

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7 hours ago, zmk1962 said:

My wife called me away to help in the kitchen with the Friday night guests special dinner prep... so didn't have time to  say...

1. I always run with a water separating filter and change it every 12months

2. My motors will clock over 21yrs and 20yrs November this year (shit where does the time go!) ... so its a testament to their manufacturer ....and to how they are being treated - they must like what I am doing.

3. This discussion about fuel additives really needs to be viewed from several perspectives like - what the motor/fuel set up is and how its used.  Which is why we are getting so many opinions - we all know what we do that works for us !

Generally, if you run a smaller capacity fuel tank that you go through frequently, maybe 87 / 91 is great. If you don't use it but can shut off the tank vent to prevent evaporation of the volatiles (creating reduction in octane) then great. But iIf you have a bigger rig with lots of fuel sitting idle, with a breather vent, then as a minimum you may need to consider whats happening to that fuel and how to maintain the manufacturer recommended octane rating.

I won't go into the implication of how fuel is produced (cracking vs distillation) and the considerations around longevity - but lets just say that fuel is largely produced for the mass market being motor vehicles - where the average life span of the fuel in the tank is significantly shorter than what you see in fuel stored in large infrequently used boat tanks. 

Cheers Zoran

Thanks for the informative post Zoran. Am I to assume that my 25ltr plastic fuel tank should keep the fuel fresh(ish) for longer if the vent (in the filler cap) is kept closed? Normally I don't have too much trouble with the fuel as I would usually manage a trip in the boat fairly frequently. This year has been terrible with insufficient water to launch the boat and subsequently, I have encountered this problem. Cheers, bn

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3 hours ago, big Neil said:

Thanks for the informative post Zoran. Am I to assume that my 25ltr plastic fuel tank should keep the fuel fresh(ish) for longer if the vent (in the filler cap) is kept closed? Normally I don't have too much trouble with the fuel as I would usually manage a trip in the boat fairly frequently. This year has been terrible with insufficient water to launch the boat and subsequently, I have encountered this problem. Cheers, bn

Hey Neil, yup the dry conditions inland have been a real bummer. Yes if the breather is closed it will keep its octane rating longer as less of the volatile liquid will evaporate... there will still be some breakdown of the fuel organic chains as some of them are inherently unstable (the manufacture process has impact here)  but generally it will last longer - in layman's terms think of the fuel as being a can of paint (a mixture of long and short organic carbon compounds) - the short ones are lighter and hence evaporate easier (being more volatile) leaving behind the longer, more dense, greasier chains - if there is a hole in the tin you get a skin forming and eventually you are just left with the dried long carbon chain - in fuel they call whats left behind resins etc.

BTW, 25L is not that much to start with and you probably have less if you have used the tank. If the fuel in the tank is not pre-mixed and you don't have a performance car, consider topping up your car tank and just filling a fresh batch for your boat.  Or just use it in the mower, whipper snipper etc. 

Cheers Z

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On 8/30/2019 at 8:34 AM, zmk1962 said:

Hey Neil, yup the dry conditions inland have been a real bummer. Yes if the breather is closed it will keep its octane rating longer as less of the volatile liquid will evaporate... there will still be some breakdown of the fuel organic chains as some of them are inherently unstable (the manufacture process has impact here)  but generally it will last longer - in layman's terms think of the fuel as being a can of paint (a mixture of long and short organic carbon compounds) - the short ones are lighter and hence evaporate easier (being more volatile) leaving behind the longer, more dense, greasier chains - if there is a hole in the tin you get a skin forming and eventually you are just left with the dried long carbon chain - in fuel they call whats left behind resins etc.

BTW, 25L is not that much to start with and you probably have less if you have used the tank. If the fuel in the tank is not pre-mixed and you don't have a performance car, consider topping up your car tank and just filling a fresh batch for your boat.  Or just use it in the mower, whipper snipper etc. 

Cheers Z

Thanks for the excellent explanation of how petrol consists of different materials which break down differently. I can now visualise what's happening in the red fuel tank. So you reckon that the "older 100:1 two-stroke" would be ok in the car??? Not high performance (Toyota Camry). Love learning from people who know what they're on about. Cheers, bn

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5 hours ago, big Neil said:

Thanks for the excellent explanation of how petrol consists of different materials which break down differently. I can now visualise what's happening in the red fuel tank. So you reckon that the "older 100:1 two-stroke" would be ok in the car??? Not high performance (Toyota Camry). Love learning from people who know what they're on about. Cheers, bn

Hi Neil, I said previously if the fuel in the tank is not pre-mixed ... then I would say it would definitely be no issue especially if you are like me and go thru a tank every two weeks or so. 

But I see you have 100:1 premix.... maybe another raider that's a car buff or mechanic can offer more input.

To be perfectly honest in the late 80's  my neighbour used to feed my stale leftover 50:1 to his 6cyl falcon and it never had any issues. But that dear Ford was a company car, and as the saying goes company cars have at least 20% more performance, carry 20% more load, and are generally more robust than any personal vehicle .... hahaha ! 

Cheers Z

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  • 3 years later...

I have used SeaFoam fuel additives for several years and have always been happy with them. I observed the dramatic improvement it made to the Yamaha outboard motor on my boat, which was already fuel-efficient. This 4-stroke outboard gas increased the MPG of my fishing boat even more, by as much as 3 miles, to be precise. This is usually a wonderful bonus for me as a frequent fisher.

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Ive been looking into fuels and various outboard requirements etc a fair bit just lately and found some quite surprising facts about it. Rather then go on about it myself I will post this video which covers fuel, engine requirements, additives and true octane ratings and how quickly those ratings can drop. The info from JB mechanical will be the most useful in regards to fuels.

 

 

Edited by JonD
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Wow, this topic has certainly dragged on.... 

Fuel and oil topics, would have to be the worst debated topics every talked about  LOL

Here's my take on it...  Fuel additives only work, if there used on pretty much fresh fuel, that's a fact. They don't lift octane rating, they will only slow it's deterioration.

I have an old Honda 3kva generator in the shed at the minute, hasn't been fired up for near 5 years. Thought I'd better do a service on it.. Before draining everything etc, I switched the choke on, 4 pulls and the damn thing fired to life and ran for 4-5 minutes perfectly, go figure, 5 year old stale fuel !!

Would I do this with my boat engine ! Hell No !  A 20 K engine compared to a 1k engine...

I've given up using additives, I didn't really see a noticeable difference when using them. I believe, that there's nothing better than adding fresh fuel, period. If I know my boat is going to sit for any period of time, I make sure the 150 ltr tank, is no more than a third full, I'll add 20 litres or so, each time I give it a start up, maybe every 3-4 weeks, then when I know I am going to use it again, fill the tank right up.  Yes, the theory that condensation will build up if you don't store the boat with a full tank, blah blah, but in all honesty, that's why we have filters. I've used this method, for decades, and never had a single fuel issue over that time.

I think we over think things sometimes, fuel additive companies, implant it in the back of our minds through clever marketing, that the world will fall in after 6 months of stagnant fuel.. Bollocks  LOL

So, my advice, run your fuel tanks down, have a 10 or 20 litre jerry can with fresh fuel, add it when you fire the engine up each month or so, and I'm picking most will have no issues at all.

As a side note, if I new I was going to have the boat off the water, for more than 12 months, I would completely drain the fuel totally, but other than that, fresh fuel is the best fuel " additive" you could ever put in your boat....

 

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1 hour ago, BaitDropper said:

I've given up using additives, I didn't really see a noticeable difference when using them. I believe, that there's nothing better than adding fresh fuel, period. If I know my boat is going to sit for any period of time, I make sure the 150 ltr tank, is no more than a third full, I'll add 20 litres or so, each time I give it a start up, maybe every 3-4 weeks, then when I know I am going to use it again, fill the tank right up.  Yes, the theory that condensation will build up if you don't store the boat with a full tank, blah blah, but in all honesty, that's why we have filters. I've used this method, for decades, and never had a single fuel issue over that time.

Yup. Said the same thing several times in earlier posts. I fill with quality 95. Top up with 95... or 98 if the boat has not been used for a while. The filters are there to handle any condensation or other crap. Regularly service the filters.

Cheers Zoran

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Hi Zoran,   To me, this is also how I have rolled over the years, with both 2 and 4 stroke engines.

At the minute, I'm only using the recommended 91 in my new 140 and although there's not been much down time, off the water as such, it seems to be going fine.

Look, dropping of Octane levels, does indeed have an effect on older type engines and needs to be closely monitored, but I'm not talking outboards as such. Older engines I'm referring to were the ones that relied on the old lead content and didn't have modern Valve timing or injection. I run a few of these and pre detonation, destroys them. But modern 4 strokes with there electronics, do compensate these issues to an extent...  I guess the real solution to all this talk, is to simply use our boats more  LOL, would solve everything !..  If only the weather would play ball and life stop throwing curve balls at us...

Edited by BaitDropper
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