Petrol mixing bottle

[Phil18]

Just bought a 14 ltr petrol tank for my rib what size mixer bottle do i need?

[1eyedjim]

As in to measure 2 stroke oil in before pouring into the fuel tank?

[Phil18]

Yes jim

[ShinyShoe]

Phil that depends on your mix. I'd assume you are on 50:1 but if the engine is really old it could be 25:1 and a few run on 100:1.

If you put 10 litres of fuel in, you add 10000ml divided by 50 for 50:1. so 1000/5 or 200ml.
If you put 13 litres in it'll be 260ml, or 14 litres 280ml of oil. BUT if its really a 14litre tank is there room for 280ml extra... It may be easier to work backwards - use 250ml of oil which will be easy to find a suitable size bottle, and put 12.5litres in from the pump.

What I find much harder is when I have a ""half"" full tank already. You have no idea how much is in there. Lets say its got 7.7litres in it and you want to top it off to 14litres. You go to the pump and add 6.3 litres. You now get the calculator out and divide 6300 by 50 and now need to find something that will measure 126ml...? Often easier to work with a 5litre can like you'd use for your car. 5litres + 100ml oil. Usually enough space to squeeze it in. Mix it, slosh it into the tank. If no room you just store the remainder in the can. Next time you fill up slosh the remainder in the tank first so you have an empty can to begin with...

[Phil18]

Cheers for that will have to do some calculations.
Many thanks

[ShinyShoe]

Oh and pick your plastic carefully - I put some unleaded in a plastic beaker (like you'd get at a beer festival) the other week. It instantly turned white and in 10 minutes had melted through the bottom (made a *** mess!) But I dread to imagine what plasticisers dissolved into the petrol...

Polyethylene would be good. Look for one with graduations engraved in rather than printed on.

[Searider]

I can't remember where I got it from but I had a graduated plastic lab beaker when I first had a boat (1980s). Held about 300ml and 50ml graduations.

Perhaps available from a good chandlery or a resin supplier?

[Phil18]

Thanks for your help will probably go to local marine shop and purchase there rather than online.
Cheers.

[dave3235]

Hi All

I use the one shot container does 5 ltr and buy a pack of 20 ml plastic shots from a £ shop.Keep to whole Ltrs and just half it for odd ltrs.Or medical syringes on ebay 100ml job done.

[Boatintercoms]

I use one of these:-

Plastic Measuring Cylinder Laboratory Test Graduated Trial Liquid Tube Jar Tool | eBay

Only put the oil in it not petrol, not melted yet!

[Phil18]

Cheers John

[jeffstevens763@g]

styl chainsaw accessories have a jug orange all marked off for £5.00

[Phil18]

Thanks for that will have a look online to order one
Cheers.

[Phil18]

Any idea on correct ratio mix for a mercury 7.5 outboard?
Cheers

[ShinyShoe]

The snag with chainsaw, strimmer ones etc is they are designed to mix small fuel quantity at a time. Like a litre.

[Poly]

Originally Posted by ShinyShoe

...and now need to find something that will measure 126ml...?

you really don't need to be that precise. 50:1 is a round number for convenience not because by some amazing coincidence the optimal ratio is actually bang on 50:1.

[jeffstevens763@g]

For what they cost have two tanks no need to guess the mix then decant when both half full to fill one tank, then mix full tank again 50-1 1litre of oil to 50 of petrol and divide for your mix and tank size some of the two stroke bottles use to have a window with a gauge to show the oil @ a given ratio.

[jeffstevens763@g]

Originally Posted by Poly

you really don't need to be that precise. 50:1 is a round number for convenience not because by some amazing coincidence the optimal ratio is actually bang on 50:1.

As poly says on a fixed ratio your burning the same amount of oil at tick over and WOT.
That why auto lube came out a little out each way not going to hurt on oil ratio

[ShinyShoe]

Originally Posted by jeffstevens763@g

As poly says on a fixed ratio your burning the same amount of oil at tick over and WOT.
That why auto lube came out a little out each way not going to hurt on oil ratio

I totally get that. But if this time your mix turns out to be more like 45:1 or 40:1 and your plugs are oiling and so next time you are a bit tight on the oil to reduce the risk of oiling, but a dodgy measure anyway means you are now at 60:1 which is a bit lean causing more wear and tear.

I'm sure 125ml rather than 126ml is fine. Afterall how did you measure the petrol volume to match up... Although fuel pump at a filling station is -0.5% to +1% accurate.

[Nick Hearne]

I bought one of these and refill it as it makes for very easy mixing!
Yamalube - Super 2 stroke Engine oil - 2-M - 1 Litre Yamaha Marine | eBay