i think i have bad gasoline. my have burnt #1 piston

[warrior1]

can 2 cycle mix become stale?
today i filled up my 6 gal fuel can from a tank i had pulled from another boat. this tank had about 10 gals of 50:1 mix that had been sitting in it for about
6-7 weeks. i added about 4 gallons of old gas to about 2 gallons of new gas in my red plastic tank.
i then proceeded to hit the lake. everything ran fine for about 10 minutes, then my engine (1978 140hp evinrude) started dropping RPMs and generally running like crap. it started surging and would not make it over 4000 rpm. i continued to run the engine for about another 20-30 minutes, but it just ran like crap. sputtering, no power, surging and low rpm.
the fuel filter is clean and the line to the tanks is good. i ran out of daylight before i could go try fresh fuel in the 6 gal can again.
not to sound dumb, but i am thinking this is simply a case of stale gas?
anyone else had the same experience?

 

[tashasdaddy]

Re: how long is 2 cycle mix good for? i think i have bad gasoline

Re: how long is 2 cycle mix good for? i think i have bad gasoline

i've used 6 month old gas but no older. are you sure the vent was open on the fuel tank.

 

[kenmyfam]

Re: how long is 2 cycle mix good for? i think i have bad gasoline

Re: how long is 2 cycle mix good for? i think i have bad gasoline

I would not expect 6 to 7 weeks for it to go bad but the best way to find out is to run with fresh fuel mix and see what happens. Dont stray to far from shore though !!!!

 

[fire7882]

Re: how long is 2 cycle mix good for? i think i have bad gasoline

Re: how long is 2 cycle mix good for? i think i have bad gasoline

Gas shouldn't go bad in 6-7 weeks. Might be water or trash in the pickup.

 

[warrior1]

Re: how long is 2 cycle mix good for? i think i have bad gasoline

Re: how long is 2 cycle mix good for? i think i have bad gasoline

thanks for the help.
i didnt think it would go so quickly, i have used 6 month old 2 cycle mix treated with stabil and had no problem. however, i didnt know how long untreated mix would last.

by the way, yes, i made sure the vent was open, i also ran it without the cap on to make sure the vent was not clogged.
i then disassembled the tank (its a cheap atwood $16 tank). swapped out the brass omc fitting on the tank and pulled the tube from the tank.
no obstructions. no difference in performance.
could water in the old gas be an issue?

i dont think there is any obstruction or junk in the carbs because i always run an inline fuel filter.

this engine ran just fine the other day on sunday.
i will try new gas tomorrow and then maybe start checking the spark plugs.

 

[BaitThrower]

Re: how long is 2 cycle mix good for? i think i have bad gasoline

Re: how long is 2 cycle mix good for? i think i have bad gasoline

could be water in the gas yes, especially if it was ethanol mix gas? Also, did the old tank have the same 2-stroke oil that you use or was it different oil? Shouldn't mix brands of oil in a tank :redface:

 

[CharlieB]

Re: how long is 2 cycle mix good for? i think i have bad gasoline

Re: how long is 2 cycle mix good for? i think i have bad gasoline

Did you remember to squeeze the primer bulb WHILE it was slowing down/running poorly?

If that improves running you may be about to rebuild your fuel pump.

 

[Dhadley]

Re: how long is 2 cycle mix good for? i think i have bad gasoline

Re: how long is 2 cycle mix good for? i think i have bad gasoline

Untreated fuel today can go "bad" in 45 days or so. However, most motors today can tolerate that to a given degree. While that may or may not be your issue you may have, as mentioned, water in the fuel, especially if you added - or had - E-10 in the tank. Even if the only E-10 you had was the new fuel it could be "cleaning" the tank and the loosened particles have to go somewhere. E-10 will attack fiberglass and some plastics.

It may not be a fuel issue at all. Could be an ignition or head gasket issue.

 

[warrior1]

Re: i think i have bad gasoline. my have burnt #1 piston

well, after working on my engine, i have figured out that it is not the gas. when diagnosing why the #1 cylinder was not firing, i pulled the plug. the electrode was bent in. soooo. now i looked into the cylinder and the top of the piston is burned, or partially melted away on the sides.
is this expensive for me to fix, and does it require reboring the block. i will tear the head off tomorrow and take a further look at it.

as far as why it burned the piston, im assuming it was maybe caused by a lean condition.
thanks in advance for any and all suggestions.

 

[emdsapmgr]

Re: i think i have bad gasoline. my have burnt #1 piston

If the cylinder is running lean, it will burn a piston. I'd pull the carb off and pull the jets for the #1 cylinder. Pull the jets out and have a looks. The high speed jet may have debris in it, restricting fuel flow.

 

[dajohnson53]

Re: how long is 2 cycle mix good for? i think i have bad gasoline

Re: how long is 2 cycle mix good for? i think i have bad gasoline

...Also, did the old tank have the same 2-stroke oil that you use or was it different oil? Shouldn't mix brands of oil in a tank :redface:

Is this true? I thought TCW3 certified oils were totally compatable.

I've never, ever hesitated to switch from one oil brand to another either when premixing in my large on board tanks, or now with a VRO2 pump/oil tank. It would have been totally impractical with the large tanks when premixing as I need to keep them topped off before starting long trips, and switch from various brands of oil depending on availability and price.

With the oil tank, it would be easier to run it low before switching brands, but certainly very impractical if not impossible to run completely dry before switching. I can't see how mixing a new oil into a small amount of previous oil would be any "safer" than just filling and mixing brands as needed.

I've never seen for myself, nor ever heard of any problems doing this or been warned not to.

 

[Dhadley]

Re: how long is 2 cycle mix good for? i think i have bad gasoline

Re: how long is 2 cycle mix good for? i think i have bad gasoline

Mixing TCW III oils is fine. I believe that part of the certification process is that they remain compatable.

 

[warrior1]

Re: i think i have bad gasoline. may have burnt #1 piston

Re: i think i have bad gasoline. may have burnt #1 piston

well, after removing the head, i found out that the piston is not burnt, but it is chewed up. it appears that part of the ring or some small,harder piece of metal entered the combustion chamber and tore it to hell. bounced around there like a ping pong ball. there are gouges all over the piston and head, but no melted aluminum.
there are gouges in the cylinder wall and a chunk out of the ports on the block.
its almost like someone took a punch or chisel to the piston top.

the spark plug is complete, except for the electrode having been pushed in from contact with junk in the cylinder.

so, i would think this is not because of bad gas.

notice the scoring and chunks missing from the top of the ports

inside of head chewed up

piston with chewed up edges. notice the top edge of piston. it looks like something forced its way through that slot into the combustion chamber.

bent electrode on spark plug, but no broken insulation or anything

any one else have experience with this and can offer a more educated answer than mine?

 

[emdsapmgr]

Re: i think i have bad gasoline. my have burnt #1 piston

One of the rings broke. The edge caught on an intake or exhaust port, further cracking the ring into pcs. The pcs worked their way into the combustion area and got compressed between the head and piston top. This type of failure can be due to carbon on the rings, a common crossfow problem. Carbon prevents the oil/gas mixture from cooling the back of the rings and they overheat and disintegrate. It's probably not due to the last tank of gas you used, but rather the general quality of fuel available today. This can be averted with occasional use of Bombardier Carbon Guard, or annual use of their Engine Tuner product. After teardown, you may find the block rebuildable, but I'd look for a new head on that side.

 

[emdsapmgr]

Re: i think i have bad gasoline. my have burnt #1 piston

An engine that is running cool for long periods of time can also cause carbon buildup on the rings. It's important for any engine to run with thermostats and come up to normal operating temps while running.