Outboard petrol "shelf life".

AFAIK, older type petrol would always deteriorate over time because the lighter more volatile ethers would evaporate quite quickly, causing ignition to became much harder. Some can even leach out through the walls of containers, so even tight sealing wouldn't help much. Wouldn't think modern fuels are much different.

Virtually all outboard manufacturers at one time started quoting 100:1 mixtures, but soon retracted the advice. Dont do it.
 
macd said:
I've certainly never had a problem with old (i.e last year's) premix. Don't have a car, the boat has no great need of a strimmer, and I'm too tight to chuck the stuff away. I periodically run the carb dry, and always drain and clean the float bowl each winter. In fact I've been known to keep the carb in a nice warm drawer.

If I can add a related question for Vyv: in the old days of pre-mix in motorcycles (when petrol was stabler, although the tetra-ethyl lead didn't always help stinkwheels) it used to be the received wisdom that while the petrol component didn't go 'off' very much, the oil degraded over time in the presence of petrol. As a former Shell man, do you have a view on this?
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No, that's a new one for me, although this is not an area I have and direct experience in. I could imagine some interaction between additives of different companies but not within one of the majors. At Thornton everything was tested, including fuel for strimmers, lawnmowers, motorbikes and a major project on chainsaws.
 
In the Caribbean cruising community it is generally accepted that once mixed 2 st fuel is mixed it has a short can life, say 2 to 3 months.

IF a small 2 st is not run for a month or so it becomes necessary to clean out the carb and fuel line before it will run normally again, possibly several times.

The Tohatsu 2.5 / 3.3 and all rebadged clones seem to be particularly susceptible. Mine certainly was.

The good news was it was often possible to limp home at 1/4 speed by juggling the throttle and choke. Mind you this could be nerve wracking when crossing an open bay with nothing downwind for a few hundred miles.
 
Thanks for all the responses.

TQA can I just ask, do you think the fuel is going off once it's been mixed 'cos if so there is an "easy" fix ... buy five litres and only mix what you think you want. Not ideal but if the fuel in the can stays fresh it's the only way of avoiding continually dumping fuel and always having to buy fresh at perhaps a litre at a time :(
 
Try putting a little modern petrol in a jam jar, and leave it to evaporate in the sun. There will be a nasty, sticky deposit.

Before this year, I used old petrol with impunity. But this year, had lots of problems.

So: I have cleaned the tanks, replaced the flexible pipes, added a proper water separator/filter in the supply pipe, replaced all the connectors, and had the carb ultrasonically cleaned. Before lay up, I ran the engine until it emptied the pipes and filtre. I have also added Quicksilver petrol conditioner to the fuel left over at the end of season. So far, this has cured the problems, but will see next year!

TonyMS
 
Previously had fuel go 'off', carburettors gum up, sticky starting etc etc had them both serviced, a Mariner 3.3 and a Tohatsu 3.5 and now just buy a couple of litres of fuel at a time for mixing that way it does get used up before it gets old and not had any problems this season.

I will give BP ultimate a try, interesting info.
 
Was with a friend when he bought a Honda 2.3 from a respected local dealer and he recommended using a fuel stabiliser, which I also bought for my 1yr old Honda 2.3. When laying up the manual says drain the carb but the dealer says don't drain the carb! On a couple of occasions my outboard has started then immediately stopped - for about 3/4 times then it ran ok - I'll mention it to the dealer when I next visit.
 
They are correct. I have proved it on many occasions. 8 to 10 week old straight fuel will lose its potential. , mixes with 2 stroke will accelerate the problem.
 
I have had all sorts of problems with my Honda 2.3 with blocked jets after leaving fuel in the carb for 3 months. Now I always drain the carb after each use and empty all fuel over winter clean bowl with carb cleaner. Given this thread I might switch to a premium fuel to see if it makes a difference.
 
Bav34 said:
Thanks for all the responses.

TQA can I just ask, do you think the fuel is going off once it's been mixed 'cos if so there is an "easy" fix ... buy five litres and only mix what you think you want. Not ideal but if the fuel in the can stays fresh it's the only way of avoiding continually dumping fuel and always having to buy fresh at perhaps a litre at a time :(
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I can not answer that as I have only have 2 strokes and buy just enough petrol for my current needs which are 2 to 3 gallons a month. 18 hp Tohatsu. The 3.3 was a back up purchased used when my 18 ate it's lower crankshaft bearing at 11 months.
 
I always drain the carb on my 2 Stroke 3.5 at the end on each session of use. It is bring transported on its side.

My other 2 Stroke 8hp was run dry at the end of last season. Last week I emplied its remote fuel tank through Dr Funnel funnel, put the same fuel back in through the funnel again, I think I added some fuel stabiliser as well. Engine started 2nd pull having not been started for nearly a year. The funnel is not cheap but is very fine mesh and does hold water back.
 
My Yamaha 5 must have a charmed life; the last time I topped up the metal petrol tank was last year (5Lt) previously it was 2004 - still runs.
 
could use Aspen ready mixed at 50:1. very expensive at £18.98 for 5 litres, but you won't throw any away as it keeps for 3 or 4 years, and it won't gum up the carb
 
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