Bad Petrol

[thomas]

Not sure if this has been covered but most outboard engineers I've met seem to think todays petrol is pretty ropey and goes 'off' very quickly, after three of four weeks, so therefore leaving your tank full is not a good idea.

I probably buy petrol for the mover every other year and store it in a can in the shed, I've had a Merc 3.3hp outboard that was sat for 3 years unused and the previous owner of my Beneteau with Merc 6hp 4 stroke only put fuel in once a year - year all three engines have worked perfectly and started first or second pull every time.

Is fuel used as an excuse for a problem when it may not be guilty, I always thought petrol was part of the separation when oil is refined so how can it go bad?

[mick]

Can't speak for the rib yet but had no problems with the sib, lawn mower or my mothers Renault Clio that stood for 18 month with half tank in and was no problem (plastic tank though)

[m chappelow]

Think a couple of months at least should be ok a lot depends what type of tank its been stored plastic or metal in and if its had it access to air also wether or not it's been premixed with oil which can have separation due to additives especially the cheaper stuff
Suppose also if it's been contaminated in the tank from previous storage eg water ingress or condensation ,venting .

Our local village garage many years ago had a problem with condensation from the atmosphere getting into the storage tanks as its down in the bottom of a ravine and prone to heavy damp air through lay of the land with a beck running past ,the new owners dident realise the water traps needed emptying much more regular than the average filling station,
If your going into remote places not a bad idea to get your fuel from 2 different sources ,or at least a busy filling station where the fuels more likely to be replenished more often

[jumpinjack]

Had this problem today, was using my main tank boat going great, switched over to me 20ltr reserve tank, engine starting smoking, and missing like mad. Switched back to main tank and she went fine.
Have had the reserve tank full for about 3 months, but this is the first time I've come across 'bad fuel symptoms' .... I suppose it's good for nothing but burning now!

[m chappelow]

Originally Posted by paulbryson75

Had this problem today, was using my main tank boat going great, switched over to me 20ltr reserve tank, engine starting smoking, and missing like mad. Switched back to main tank and she went fine.
Have had the reserve tank full for about 3 months, but this is the first time I've come across 'bad fuel symptoms' .... I suppose it's good for nothing but burning now!

How about old fuel just being left in the fuel line or primer bulb and not in the tank that's made it iffy when switching over

[Erin]

I've never noticed a problem with either my car or outboard using old fuel, but my mower gets a bit sensitive. I think modern fuel injection and ecu's can cope with suspect fule with lower octane and compensate whereas an old carb setups are a bit more pernickety.

[SIBer]

For every forum poster staying "never had a problem" there is another saying "had a problem". I guess it depends on the original fuel, temperature, humidity and other factors. Some fuel stabiliser (e.g. Stabil, Briggs & Stratton, Quicksilver) is a cheap way to prevent any problems. I always use stabiliser in my small engines.

Same goes for spark plugs, change them regularly or have them running for years.

[thomas]

Agree about the plugs, guru Bill Mitchell swore blind my plugs were ok and not the cause of a problem, for the sake of a tenner I replaced them and my problems went away.

Fuel left in lines can cause a problem as it leaves a sludge behind that can get into the carbs, if, if you have them, and block things, but that's not bad fuel and needs to be left a long time to happen. With my tender I used to turn the fuel off and run it mainly as it used to go in the car but was taught to do it.