Unleaded fuel

[rbrooks]

The Goverment here is talking about doing away with leaded petrol, I use an air cooled 3.5HP Yamaha o/b on my boat, I dont think unleaded will affect the running of the engine due to the two stroke oil. or will it?
I've heard stories that unleaded mix does not store for long? is this true because I baut 20L petrol (leaded) last year and still have 6L left, will I be able to do this with unleaded?

R

 

[ccscott49]

In a two stroke, it doesnt really matter if you use leaded or unleaded, especially in a small ouboard, the octane rating of standard unleaded should be high enough, if not you can retard the ignition a little to counteract it, you do not have to worry about upper cylinder or valve lubrication. You shouldnt really keep petrol, mixed or otherwise for too long, as it starts to form a varnish or gum, which forms little balls, which plug things up, six months is I know is OK, but a year?, maybe too long. Only but enough for a month or two at a time.

 

[Guest]

I struggle with this as well, you can't only buy enough for a month or two as then you don't have any spare in case you have to do that long motor back if there is no wind. I got caught like this the other day and only just had enough for the trip back from Moreton Is. I usually keep a full tank and then swap it for some beer every few months with a mate who has a stink boat and uses heaps. If I don't have a long motor during he year like last year I only used about 10 litres total in the whole year despite going away about 18 times for the weekend.

 

[rbrooks]

Good idea I've got a mate who will swop fuel for beer, How many beer's per litre??

R

 

[Guest]

It varies depending on how much I can drink on the night. The friend in question lives around the corner, so I wander around there with the near full can of fuel, we proceed to get pissed until his wife kicks me out for swearing too much, then I wander home with the empty fuel can. We're getting clever at it now as we have worked out that it's a lot better to transfer the fuel BEFORE we get maggotted. John then often follows me home prefferring my company than the trouble and strife whereupon we attack my fridge. I'm sure I lose out overall but hey we have a bucket of fun in the process.

 

[oldharry]

How many litres per pint?

Engines vary enormously as to how they cope with stale fuel. What happens is that even in sealed containers the more volatile fractions evaporate off, and the chemical composition breaks down, reducing the flammability. The higher the compression ratio of the engine (plus several other factors such as combustion chamber design and designed ratio of fuel to air in each charge) the more difficult it is to get the stale fuel to ignite in the engine.

It is well known in motorcycle circles for example, that many higher performance machines will not start if fuel is left in the carburettors for more than a week or two. Hondas were notorious for this. This also has something to do with the carbs themselves, but these highly strung engines cannot cope with fuel that has been left standing for even a short time!

There was an interesting posting some time back from a gentleman in the petroleum industry explaining it all properly, and suggesting petrol should not be stored longer than 3 months. In practice most smaller outboards will run on petrol six months old, in my experience. After that you may get starting and running difficulties, unless you own a Seagull, which will run on almost anything (and no I am not a Seagull fanatic!).

But why bother with fuel/ beer swaps? If you are keeping a large fuel reserve, only mix the 2 stroke 5 litres a time, then put the surplus in the car every few months. (Just dont try putting the beer in as well....)

 

[ccscott49]

I knew I had read somewhere about that storage stuff! Just couldnt remember where!

 

[Guest]

And miss out on those drinking opportunities?....No way.