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Old 19 August 2012, 18:47   #11
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I feel for you . Put 13l in a 22l tank that was before the addition mixed to about 50:1.

So how much oil did I need for 13l ? Three of us stood and looked at each other for about five mins just confusing ourselves .....so we stuck 'about' 250ml in and sped off into the sunset - read pub at Wareham ( it felt fast anyway )

Turns out we were about right ...
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Old 20 August 2012, 04:07   #12
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Quote:
Originally Posted by jwalker View Post
So if you fill the tank, how're you gonna find the space to get the oil in?
That's my problem in a nutshell. I don't know exactly how much fuel is in there and if I fill to the top and assume that the tank holds 22.7 as stated on the tank itself then I've no room to add oil.

Thanks for all your suggestions though, it's appreciated. I'm going to assume 20 litres approx is still in the tank and add oil accordingly. If the worse that can happen is a smoky engine for this tank of fuel then that's fine. I'll be refilling it soon enough anyway as we've got a weeks lost boating to make up for. :-)
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Old 20 August 2012, 04:38   #13
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Hi

have a look at 2 Stoke Oil and Fuel mixture chart | Glasgow and Clyde Outboard Services Outboard Engine Servicing

I also like the little measuring jugs that has this information on the side i.e. where to fill to for 50:1 and 100:1 engines.

Dave
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Old 20 August 2012, 05:07   #14
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Isnt it easy

50L of fuel = 1 Ltr of oil
25L of Fuel = .5 ltr of oil
so
20L is about .45 ltr of oil ish.

or am I missing someting?
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Old 20 August 2012, 07:55   #15
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Hi Jezza,

Unfortunately my problem is that I don't know exactly how much fuel is in the tank as it's been leaking out of the end of the pipe, maybe something to do with the heat? I put 20 litres in it 6 days ago.

Cheers
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Old 20 August 2012, 09:03   #16
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i see ok the tanks do this if you dont keep the vent open.
fuel gets pushed out as the tanks gets pressurised as the fuel expands/evaps.
so simple.
fill it up.
check for leaks.
then add in the 2st oil. Simples.

:-)
Its always best to put the 2st oil in when you fill it up. that way you cant make the mistake of not putting it in later and having a seize up. !!!

best to have too much than not enough oil.

so fill it up and add in the 1/2 Ltr or oil :-)
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Old 20 August 2012, 09:09   #17
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Bottom line -

too little oil = siezure risk at WOT.
too much oil = it smokes.

If it were me, I'd err on the side of smokey. Once the tank is empty, pull the plugs, clean any excess oil, Carry on.

Your problem with "just top up" will be if the air pressure has forced fuel out "en masse" as happened to me a while ago when the ball seal on the connector failed to seat properly, as that will have pushed the oil out with the fuel.


Alternative view - it's a portable tank. Just burn what's left in there, which will at worst be sli-i-i-i-ightly too oily if the petrol has evaporated. OK, so you have a couple miles less range due to there only being 21.9L in there, but is that a problem?
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Old 20 August 2012, 09:39   #18
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Quote:
Originally Posted by jezza2011 View Post
i see ok the tanks do this if you dont keep the vent open.
fuel gets pushed out as the tanks gets pressurised as the fuel expands/evaps.
so simple.
fill it up.
check for leaks.
then add in the 2st oil. Simples.
as per previous posts (i) "Full" in 22.5L tank can be over 22.5L total volume so no closer to knowing the total volume; (ii) if genuinely full there will be no space for the 0.5L of oil.

Quote:
Its always best to put the 2st oil in when you fill it up. that way you cant make the mistake of not putting it in later and having a seize up. !!!
Whilst you mitigate that risk you do introduce other potential problems: e.g. a spillage/leak like this is then an oily (slippy) spillage; if e.g. he never used the fuel (as has nearly been the case because of other issues) he had a load of fuel with oil in it - without the oil stick it in the car, with the oil? Does he keep it? Risk it in the car? Bring in back home (its probably dangerous goods on the ferry/chunnel) etc. Long term storage of premix is a problem compared to fuel on its own; Swapping fuel between boats with 2 str / pre-mix / autolube / 4 stroke [when cruising in company or at a club etc] is easier if you don't premix until the fuel is about to be used... ...so I would suggest it is not "always best to put 2 stroke in when you fill it" and certainly not much help to the OP now.

Vincent - unless you have lost a whole load of fuel you really aren't going to notice. If you add 400 mL of oil (the correct amount for 50:1 with 20L) and actually only have a ration of 37.5:1. If you've lost more than 5L you'll know by sight or lifting the can. More likely you have lost less than a litre. So your ratio would be 47.5:1 . Most people probably aren't that precise in measuring either the fuel or oil to get it any better than that anyway. Most engines will run on 25:1 but smoke like mad and possibly the plugs foul at low revs [indeed your engine may well have been run when new in at 25:1 for the first couple of tanks full]. Some engines being used in environmentally sensitive places will run on 100:1, and although most people in the UK are scared of that number in premix (my autolube seems to use a little less than this ratio averaged out); you could probably get away with running a single tank at 100:1 on an engine that has been well lubed for all its life so far, with no ill effects. i.e. what I am saying is you probably have less that 10% error on your ratio, and even if it was 50% you would probably be fine.
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Old 20 August 2012, 11:23   #19
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I haven't seen it mentioned, but most all portable fuel tanks have a fill line cast into them. This leaves enough room to top up with oil.

If it were me, (Assuming the tank has zero oil in now) I would fill it up with gas, then top up with the "correct" amount of oil.
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Old 22 August 2012, 11:00   #20
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Originally Posted by Vincent Vega View Post
We've towed our SIB to Spain and on our 1st day, even before we got the boat in the water, we found a problem with the front tube. It's taken me a week but I found somewhere to have it repaired and i'll be collecting it tomorrow with the intention of launching tomorrow evening.

On the 1st day we arrived I filled the tank with 20 litres of fuel with the intention of adding oil at a 50 to 1 ratio. The fuel tank has sat in the shade for the past week but I've now found that fuel has been leaking out of the end of the hose. This has completely messed up my ratio calculation as I have no idea how much fuel has been lost.

Is it therefore better to overcalculate or undercalculate the ratio? Alternatively should I just discard the fuel and start again. We've already been without the boat for the 1st week of our holiday and the last thing I want to do is cause any problems with the engine for the 2nd week of our holiday.

Any ideas or suggestions?

Thanks.
Hi Vincent, Be careful with the coupler at the end of the hose, if its leaking now with no pressure its definately going to leak when you prime it. Outboard pumps rely on a sealed system and if you havent got a good seal your going to get running problems as well as a great big oil and petrol slick following you. As for the oil mixtur adding a little extra oil wont make much difference
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