Outboard petrol "shelf life".

Bav34

Bav34

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Over the last few years my Mariner 2.5 had become very temperamental, only running by juggling the choke lever.

I had it serviced last October by a really reputable company ... I had heard that they were good and even checked on here and saw no complaints so this is NOT a dealer rant.

May this year I filled it with service station petrol and ran it around the marina at less than half throttle and it was fine.

We didn't use it again until August and the old problems had returned ... unwilling to rev high and a tendency to stall.

I contacted the company and they said it was either old fuel or dirt in the carb.

The fuel was spotless when I topped up and was only 10 weeks old.

I drained the May fuel out and put in new fuel.

Same problem.

I took the outboard into them today and they were adamant that petrol now goes off between 8-12 weeks and needs dumping after that period.

They put the fact that the new August fuel hadn't cured the problem down to to the carb already being gummed up from the May fuel, despite me (always) running the carb dry.

What do you think?

Do you have the same problem if you rarely use your outboard? What about lawn mowers, petrol driven chain saws etc.

Are there thousands of people dumping fuel that I know nothing about?

Here is a vid. for your entertainment :)

 
we have the mercury equivalent of your engine and have experienced same symptoms - whilst on summer cruise bought spray can of carb cleaner and dismantled carb to clean it out since when it has been fine (although we now haven't used if for a couple of months so problem might be back ) like you we have always run engine dry before stowing it - on strip down there was dry deposits almost powdery in the float chamber - not sure there is a solution but be interested to find out - struggle to be convinced petrol goes off that easily as - as you mentioned- the can in the shed for the lawnmower lasts all year and the petrol in our kit car is rarely refilled and it seems fine even when left for months unused
 
I am currently using fuel in my Tohatsu 3.5 2-stroke that was bought and mixed at the beginning of the 2015 season. It runs perfectly well on it. I did experience a severe reluctance to start at the end of last year but a new spark plug solved the problem.
 
I was concerned about the advise ability of using "old" fuel in my outboard (Tohatsu 3.5). My usual method of disposal is to add the stuff to fuel when topping up my Morris Minor (waste not.....) This year I discovered a gallon of mixture that must have been around 3 years old at least. I used it to top up my garden strimmer and it was fine, albeit a little smokey. The carb in the strimmer is so much smaller than the outboard which is therefore much more susceptible to gumming up. It is also impossible to run completely dry. I've quite a history running old strokers from Bantams to a really clapped RD250 so I always go first to the plug, the the exhaust before thinking about the carb. I try to buy "old school" mineral 2srroke oil. Could that be a contributory factor? Sediment suggests "dirty" fuel to me. "Gum" looks more like a thin lacquer in my (more recent) experience.
 
Although my outboard is different, its a Suzuki DF2.5, a 4 stroke, I've just finished a 5L can of petrol bought at the start of the 2015 season. I've not had any starting problems.

I also run the engine dry of fuel on tick-over at the end of each trip and drain the carb' bowl at the end of the season, along with running it in a bin of fresh water and changing the oil.

I find it hard to believe the petrol goes off, if stored in a sealed container, in a way which causes starting problems with an outboard.
 
In my experience its nearly always partially blocked (jets) in these small two stroke outboards. Spraying carb cleaner through removed jet may not shift it. I would buy a micro drill bit set from Machine Mart (£10) and run the drill bit that corresponds to the main jet size through the jet. Or, just find a Tohatsu/Mariner stockist and order a new main jet. Very cheap part so worth a try surely?
 
That sounds like an outboard problem not petrol, I've used petrol in a mower and chainsaw over a year old with no problems. I do change the spark plug when I start using either of them spring for the mower and autumn for the chainsaw.
 
My two stroke mixture is from March this year (8 months). I always give the feed can a very good shake before plugging into the engine, and fingers crossed have never had any issues upto now.
 
My petrol which is used for the 4T outboard an the suitcase generator is getting on for 3 years old now. Both outboard and generator start first pull although both are run dry / carb drained at the end of each cruise.

Richard
 
After a recommendation from my garden machinery engineer who spends most of his time repairing the damage old fuel can do to fuel lines in petrol strimmers and the like I now put a fuel stabiliser into my garden motors and tender outboard particularly when they are not used over the winter.
It protects against the damaging effects of the ethanol in todays fuel. Plenty of products around and I have not had a problem since using it.
 
Modern petrol contains a percentage of ethanol which causes petrol to go off relatively quickly and also gum up carburettors if left wet. I always use the BP ultimate which it is said contains no ethanol. I also use it in the lawnmower and have had no problems with either. Addatives are also available to overcome the ethanol.
 
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?
 
macd said:
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?
Click to expand...

For the first few million years of its existence the oil spent 100% of its time in the presence of petrol. :)

Richard
 
If the outboard (Suzuki 2.5 and Honda 2.3) has not been used for many months I sometimes get starting problems. My first action is to drain the petrol out and replace it. I always notcie the old petrol has a yellow tint to it. The new petrol I put in is not new but from the same container of fuel last used to fill the outboard. i.e. It keeps much better in the fuel can and is still clear when I put it in the outboard.
 
I've been led to believe that when you mix oil and petrol it actually becomes a new substance, so there's really no 'oil' to deteriorate. But I may be wrong......
 
Bav34 said:
I took the outboard into them today and they were adamant that petrol now goes off between 8-12 weeks and needs dumping after that period.
Click to expand...
Meanwhile in the real world; I am still using a 5 ltr can that I filled in 2014.

When putting the engine away I turn off the fuel and when the carb empties the engine stops.
 
I have no claim to be a petrochemical expert, but a couple of years ago I tried to start my Tohatsu 3.5 and couldn't. I took the cap of both the fuel tank and the fuel can, and the smell was like old paint or white spirit rather than petrol. I tipped it out, replaced with fresh and it started second pull. The moral from personal experience is that outboard fuel goes off. That fuel was only about 12 months old.
 
I keep the 2-stroke o/b fuel on board in a can already mixed (about 75:1, it will run on 100:1 but I worry), it's a Tohatsu 3.5 and it runs happily all season even if the fuel is 5-6 months old. I always run the carb dry when I stop for the day, and drain the tank at the end of the season.
Any fuel left at the end of the season goes in the can for my Honda 4-stroke mower which will run happily on that during the first part of the following year, albeit it a bit smoky but then it would be. Again I run the mower carb dry at the end of each session.
 
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