PDA

View Full Version : 2 Stroke Fuel



squire
14-05-2002, 06:06 AM
I was wondering if anyone would be able to tell how long 2 stroke fuel lasts after it is mixed? I have heard people often say that it taints but not sure what this actually means?

dnej
14-05-2002, 06:22 AM
Give Shell a call,the say 30 to 45 days tops. Old fuel cause the motor to run hot, and also gums up carbys etc.Apparently old fuel is the cause of a great many motor problems. Bit of a buggar isnt it?
Regards
David

adrian
14-05-2002, 07:44 AM
hi
the gumming up of 2 strokes is due to the petrol in the carbie and lines vapourising leaving the oil
behind after a while this slowly goes tacky thus gummed up
i only try to refuel when I go out so the tank is full as the boat hits the water . on the older models you can disconect the feul line and run it dry to stop the carbie from gummy up don't try it on the new types ( don't know what will happen) check with dealers on how to stop it

anzac

Kerry
14-05-2002, 01:46 PM
I'm not for running motors out of fuel (premix or injected) as I think it's a very bad practice especially for larger motors for a number of reasons and serves no real purpose.

Fuel doesn't have a real long life at all and mixed with 2S oil only reduces it life further. Old fuel is not all that friendly on pistons and these days fresh is always best.

Cheers, Kerry.

pjw200371
22-09-2006, 10:15 AM
Is there any product you can add to your fuel (similar to Spitfire for your car) that will clean the carby/fuel lines of 2-stroke motors?

steveg1100
22-09-2006, 01:48 PM
I have not used it yet but I have come across a product called moreys upper cylinder lubricant. It claims on the bottle that it can be used with two stroke engines. I am sure that someone on this forum would have tried it and will let us know if it worked.

honda900
22-09-2006, 06:34 PM
johnson has a product called engine tuner to address such issues.

http://parts.evinrude.com/info/parts/engine.html

Regards
Honda900

stevedemon
22-09-2006, 07:56 PM
Hi all morleys is the better one for 2 strokes i use it on mine a 115hp yamaha 89 model just check to make sure you do not over use it per tank

Cheers ;D ;D
Steve 8-) 8-)

BaysideMarine
22-09-2006, 09:30 PM
Squire, according to Mercury, fuel begins to degrade (loses octane, or potency, or more accurately its ability to withstand compression before spontaneous combustion) in about 14 days.

By 2 months its useless.

Sure your engine will run on it. Later model, lower compression engines will cope slightly better on stale fuel and older Mercs with fin top pistons are deadly on stale fuel. They will chew the top right off the piston......

In short, stale fuel means it cannot withstand as much pressure (compression) as it did when it was new. This is important because the now degraded fuel will cause DETONATION. This is a destructive scenario where the fuel charge is prematurely ignited before the sparkplug fires. It results in 2 flame fronts, one from the spontaneously detonation and the other from the spark plug. These 2 flame fronts collide with destructive results.

If you need a use for your premixed fuel it makes awesome weed/grass killer.... Takes about 30 mins or less for the area you spray to die off......

Cheers

Fat_Chilli
22-09-2006, 09:49 PM
Does this also apply for un-mixed fuel sitting in the tank? My 90hp 2 stroke is oil injected and I have 80 litres thats been sitting in the tank for just under 3 weeks.

Cheers

FC.

BaysideMarine
22-09-2006, 10:18 PM
Applies to all fuel Chilli.

As I understand it, fuels degrades more rapidly than I stated if its mixed.

Also, dont believe the common misconception that topping up the tank with premium will offset the degraded fuel. It wont.....

Its due to some oxides that are procduced as by-products of the degrading fuel and they cannot be counteracted by adding higher octane fuel as they are a new substance once they are created.

I think your 3 week old fuel will be fine. If it were 2 months old I would say don't use it, but 3 weeks will be ok.

This is why its very important to never fill up at out of the way petrol stations that likely have low turnover of their fuel.

Cheers

troy
23-09-2006, 11:24 AM
I have used fuel older than 2 months and i never had a problem.
It was my previous motor being a 130 hp Evinrude and i had it for 8 years.
I might be lucky but i know of heaps of people up here that do the same.
Just my thoughts and i think the idea off tossing out fuel that is 6 weeks old is going over the top.
Probably have put a curse on myself now.
Troy

newchum
23-09-2006, 11:42 AM
troy,
i have 1985 evindure that still ran the vro until mid this year. i was covinced by mechanics to change to premix. never had a problem with old fuel , even 6-8 weeks old.
now on premix if the fuel is more than two weeks in my tank the old girl plays up. makes me wonder how long it sits in the tank at the servo. they certainly don't empty out the tanks and refill . or is there a reason it doesn't go of in there tanks

ryank
23-09-2006, 03:22 PM
dont use it after about 3 months. if u use old fuel it goes like varnish in the carbs

troy
23-09-2006, 03:28 PM
troy,
i have 1985 evindure that still ran the vro until mid this year. i was covinced by mechanics to change to premix. never had a problem with old fuel , even 6-8 weeks old.
now on premix if the fuel is more than two weeks in my tank the old girl plays up. makes me wonder how long it sits in the tank at the servo. they certainly don't empty out the tanks and refill . or is there a reason it doesn't go of in there tanks
Newchum,
Sorry if i mislead you but i should have stated my fuel was not mixed.
Troy
I am a bit confused did you just recently disconnect and start mixing your oil yourself.
With oil injection the fuel in your tank would not be mixed.

newchum
23-09-2006, 07:26 PM
troy
i ran the evinrude vro until i was talked into using premix.(every outboard mechanic said it was a breakdown waiting to happen) i still have the vro fuel pump connected but the oil circuit is disconnected. i buy 50:1 premix at the servo

BaysideMarine
23-09-2006, 10:04 PM
I have used fuel older than 2 months and i never had a problem.
It was my previous motor being a 130 hp Evinrude and i had it for 8 years.
I might be lucky but #i know of heaps of people up here that do the same.
Just my thoughts and i think the idea off tossing out fuel that is 6 weeks old is going over the top.
Probably have put a curse on myself now.
Troy

Troy, every time this topic comes up either here or on fishnet there is always plenty that come out of the woodwork to say they use old fuel and suffered no ill effects.

Fair enough and you have been fortunate. But it is prudent and responsible for those in the industry to advise the public of the manufacturers recommendations.

It depends to a small degree on the type of engine, be it a loop charged or crossflow engine and then piston design also. If the engine in question was an older crossflow Merc with the high fin pistons you will melt pistons almost immediately with bad fuel.... Other factors such as propping, power to weight ratios and loading are also important elements.

But detonation due to stale fuel is real and it destroys engines.

Cheers

BaysideMarine
23-09-2006, 10:22 PM
Re the disconnecting the VRO......

If you have the first released VRO (in 1984) it has no warning system chip fitted and hence, if it goes bung you wont know till you seize the engine....

However.... if you have the next released VRO which is clearly evident by the almost matchbox sized "box" sitting on the back of the VRo with wires coming from it. Early versions have 3 wires, later versions have 4 wires.

If you have a VRO engine with the electronics attached then they are wired to your warning system and as long as your buzzer works (easily tested) then keep your VRO connected.

Cheers

NTMID8
16-06-2010, 08:16 PM
Sorry to bring an old thread back from the dead but.....

I am fitting an underfloor fuel tank to my boat, i have the space to go as large as 120ltrs but am thinking closer to 70ltrs, i have a 2 stroke evinrude with the VRO disconnected (premix) so how do i go if i dont use all the fuel in my tank?
How do people with 150ltr plus underfloor tanks go when they dont use all there fuel?
My warning horn works (beeps when i start the engine) should i have the VRO reconnected?

Steeler
16-06-2010, 09:07 PM
I have only ever owned old Mercs with the high crown pistons and used fuel that has sat for up to 45 days with no detonation problems of the piston.I do use Stabil as a stabilizer and reckon this is a great product for preserving fuel for both outboards and outdoor power equipment.

Steeler

BaitThrower
16-06-2010, 09:23 PM
Fuel Doctor is another great fuel stabiliser/conditioner that will keep fuel longer (prevents gumming/varnishing and helps disolve water and other furl bug in the fuel too).

gr hilly
16-06-2010, 10:23 PM
i use all my fuel left over from my boat in my ride on, chain saw, push mower, and work vans, the mrs old holden, whipper sniper, and i find it makes a great upper cylinder lube.you can get out and walk on land.

hilly

dnej
16-06-2010, 10:32 PM
well Hilly, you are heading for trouble. You cant, and shouldnt use , two stroke oil, , which is meant for water cooled engine, in an air cooled engine.
You need completely different two stroke oil.
David

DATCOL
16-06-2010, 10:38 PM
I ad proma fuel treatment hav 200 leters under floor has sat for up to 6 months
with no problem 135 hp mariner oil injection 1994 model
COL

NTMID8
17-06-2010, 06:24 PM
So as long as i add this fuel stabiliser i should be ok? Does anyone know what the build tolernace was of a 93 evinrude (silly question but i see the merc's had strong pistons, maybe the rude did too....)

Steeler
17-06-2010, 07:02 PM
A lot of the older merc piston failures can be put down to incorrect timing particularly the inline 6's

Steeler

gr hilly
17-06-2010, 07:26 PM
after reading some remarks on this thread i am looking at buying a new motor soon would it be wise to buy a 4 stroke motor this would have to do away with some fuel problems surely??.
Hilly

NTMID8
17-06-2010, 11:16 PM
after reading some remarks on this thread i am looking at buying a new motor soon would it be wise to buy a 4 stroke motor this would have to do away with some fuel problems surely??.
Hilly

My understanding is it doesnt really matter so much about the premix (2 stroke) as much as it has to do with the fuel going stale.

Spiderpig
19-06-2010, 06:03 PM
I have a merc 150hp EFI and a mariner 30hp carb both about 3 yrs old 300 hours each. I run spitfire in both motors when they need it but for different reasons.


The 150 EFI 2 stroke is not mixed fuel and doesnt make the engine run rough, but I do notice very reduced fuel consumption. If there is still a lot of fuel in the tank when I am ready to fill up I add a bottle or two of spitfire and top up with premium. (its a 260L tank) - this seems to pick consumption and range up a lot.

The 30hp runs rough whenever the fuel is more than about three weeks old, I add 100ml of spitfire to a tank. As soon as the fuel out of the line is burnt, the fuel in the tank is like fresh fuel. I can comment on consumption though as it uses sf all. My only other advice there is use premium and only fill up as much as you need.

cormorant
20-06-2010, 01:31 AM
http://www.wynnswa.com.au/download/78701PS.pdf
http://www.wynns.net/product_files/Spitfire%20Octane%20Boost%2043804%20PIS.pdf

Here is what's in it

http://www.wynns.net/product_files/Spitfire%20Petrol%20Treatment%2078701%20MSDS.pdf

http://www.wynns.net/product_files/Spitfire%20Octane%20Boost%2043804%20MSDS.pdf

You can not " sweeten" stale fuel. It degrades from the minute it goes in your tank.

You can up the octane but it may still leave you with waxes and gums in your fuel system or it may dissolve them and clog your filters.

Some of the treatments can mobolise water from the tank but if that fuel is then left in the injection system it can come out of solution and cause corrosion issues

Phone your petrol distributer and ask them what fuel stabiliser they suggest and put it in every tank of fuel you are not using in a marine environment within 14 days. They supply stabilised fuel to marinas and remote communiies so will know.

BM
20-06-2010, 07:28 PM
A lot of the older merc piston failures can be put down to incorrect timing particularly the inline 6's

Steeler

I have to disagree with you there Steeler.

True enough, when doing a rebuild of a straight 6 Merc it is/was normal practice to fit the next size up main jets and knock the max spark back by 2 degrees and drill it into the customer that they must use the highest octane FRESH fuel possible.

This was more or less insurance for the rebuilder to avoid a comeback from detonation.

In their day, straight 6 Mercs did not suffer from detonation in any noticable volume. This is logically due to fuel in those days being superior to todays blends.

In fact, the introduction of unleaded fuel into the Australian market saw a spate of detonated engines. A good friend and mentor of mine (from Mercury) was involved in the examination of what was going on with these high fin, crossflow engines blowing up all over the place. They eventually discovered it was the lower quality of the unleaded fuel that was causing the premature engine failures.

Timing is not typically something that people will fiddle with on their engine as most people do not understand how outboard ignition works and therefore don't go fiddling with it. Of course some people no doubt do.

Cheers

gr hilly
20-06-2010, 09:44 PM
after reading some of these posts ive been put off buying an expensive new motor ill buy a second hand one and when it chits its self from the crap fuel ill get another. problem solved.

hilly

Steeler
20-06-2010, 09:51 PM
That was my point,back the timing off and they won't detonate a piston.

But a have to disagree with people not tampering with timing.

BM
20-06-2010, 10:13 PM
That was my point,back the timing off and they won't detonate a piston.

But a have to disagree with people not tampering with timing.

Yes, true, retarding the timing helps to ease detonation issues but only due to the lower grade of fuel today compared to when those engines were built.

Sure, some people will fiddle with timing but I have found "fiddled' engines to generally be few and far between. But the experience of others may well differ substantially.

Cheers

Flex
21-06-2010, 07:33 AM
Maybe we're all a bit paranoid on this topic? Fuel has been "destabilised" since 2006 I believe. How many engines have you seen blow up from this?
I haven't heard of anyone having issues directly related to old fuel.
Sure you get alot of water in fuel issues etc, but none I've heard from old fuel(within reason)


car engines sit for months and months with old fuel and run fine.

Sure it doesn't hurt to try your best to use fresh fuel,And in a boat its better to be safe than sorry.
but your average bloke cant afford to tip out his100l of left over fuel every 14 days if you dont use it.

While I always try my best to use fresh fuel its not always practical. And if my motor lasts only 15 years instead of 20 years, i dont care. Because 15 years of throwing out 14 day old fuel would probably pay for 2 more motors anyway :)

cormorant
21-06-2010, 12:22 PM
Modern cars have sealed tanks and fuel systems hence the hiss when you open the fuel cap. Boat fuel tanks are open and don't hold in the light volatile elements with expansion and contraction with surge and temp changes and attract moisture. Car fuel systems pollish the fuel by constantly pumping it through the filter and cooling the injectors, pump etc.

Older motors were no where the performance that new motors on boats are with every last HP and as little pollution as possible

A ar motor runs at much higher temps than a outboard which changes quite a few dynamics in the motor

Older boat motors were able to cope with different fuels as they wern't so finely tuned to the nth degree and modern motors use electronics to monitor fuel with oxygen senssors, TPS and computerised ignition curves etc.

Lead in fuel was not only a octane booster but changed the whole way fuel ignited, stability ,burnt and lubricated the upper cylinder.


Motors die from a combination of several things generally when a couple or 3 ducks line up motors die. Fuel is now one of those ducks always there so if one other issue happens.

cormorant
21-06-2010, 12:33 PM
deleted as a double post with site or internet response being slow

Chimo
21-06-2010, 02:04 PM
So where ?do we source / how do we add a little lead essence back in the boat fuel to regain these lost features?