Fuel Left in Motor ???

[ocbassman]

After a day of fishing I always disconnect my fuel hose from my Motor (9.9 Mariner) and let it run until it dies.

My question is .....Is this ok to do or should I leave gas in the Carb and why?


Thanx for any input
Tim

 

[tx1961whaler]

Re: Fuel Left in Motor ???

You will get many different opinions on this question.
I run mine out on my single carb motors if they will be sitting for more than a couple of weeks. I shut it off as soon as I detect that it is starting to run out of fuel (the motor speeds up).
I would not do it on a multiple carb motor, as one will run out before the others.

 

[sho3boater]

Re: Fuel Left in Motor ???

I never bother unless it leaks out and I don't want it to. I only run it out when it is going to be stored over say three months. Other stuff I will run premium in last tank and store it up to 6 months if I want to leave fuel in it for some reason and know I will use it again for sure. Some things with aluminum carbs you have to drain the bowl or it reacts and will not start, if you leave one stored a long time (3mo+) draining the bowl is the most important thing to do it can gunk up the jets.

 

[Silvertip]

Re: Fuel Left in Motor ???

Fuel does not have to be drained for storage. Fuel will not react with the jets or bowl and premium does absolutely nothing to prevent gum and varnish build up. In fact premium fuel is not needed at all and not even recommended for an engine that requires 87 octane. For long term storage, treat the fuel with a fuel stabilizer such as SeaFoam or Stabil. Run the engine long enough to ensure the mixture has reached the carb and you are done. Fog the engine if you wish. For even better protection, run SeaFoam in every tank of fuel to prevent fuel system issues in the first place.

 

[sho3boater]

Re: Fuel Left in Motor ???

After 6 months premium will have a higher octane than regular, that is why I would put it in something that needed over 87 octane. Fuel will react in a carb be it the metal or the venting, that is a fact. I worked at an equipment dealer and I knew certain equipment would not start without draining the carb. It didn't take too many tries and you realized it was way faster to just drain it to start with. Some things it will, others it does not. It always keeps better in the tank though.

Some of us don't want to afford or trouble with putting an additive in every gas burning device we have, it would take me all day. I can count 15 off the top of my head. I've used it before but I don't like to in a boat because the fuel still deteriorates and I will never run old gas in a 2 stroke outboard. I did use additives with premium fuel when I had an I/O and the gaskets in the holley carb would shrink if I drained it. It ran fine on the old gas that way, I just left a couple gallons in it.

 

[Silvertip]

Re: Fuel Left in Motor ???

Nonsense. Up here in the tundra boats are layed up for six months of the year. Some folks chose not to treat the fuel but most do. If fuel bothered equipment layed up for six months or more of the year, there would be collector cars and lawn mowers, weed whips, and chain saws laying dead in every garage in the spring. It simply doesn't happen. The expense of treating fuel is a small price to pay for a clean fuel system. SeaFoam is six bucks a can here. You don't need a full can as a preventive measure and it takes about 30 seconds to add it. If fuel reacted with the float bowl the bowls would all fall off the engine since they have fuel in them all summer.

 

[Lion hunter]

Re: Fuel Left in Motor ???

It's the ethanol that is reacting with old fuel and vent hoses, gaskets ect. I have never had the problem with that happening on the new alcohol resitant fuel lines. Octane does nothing to preserve fuel, it just retards ignition. Now there is some higher octane fuels you can get without ethanol in them. That's not a bad idea for the last tank of the season. As far as premium fuel goes theres nothing prmium about it. It's a sales gimmick to make people think they were getting better fuel. On the old muscle cars that ran 10:1 or higher compression, or some that run in hot desert heat it was needed to retard ignition and stop pinging.

 

[sho3boater]

Re: Fuel Left in Motor ???

Octane deteriorates with age in storage, look it up. In case of wanting to store it a higher octane fuel will have a higher octane after storage.

Ok, one of you take a 14hp kawasaki vertical engine found on many walk behind lawn mowers, let it sit in a warehouse for 6 months, and you pull start it I dare you. (A great engine otherwise btw) It will never happen until you drain the carb, I dealt with hundreds of them in addition to being a small engine mechanic before that and seeing it with other equipment. True with most things you can let them go six months with no problems, just with outboards (at least 2 stroke outboards) the risk of an issue is greater: you might blow the motor unlike with lawn equipment. It could be very expensive. A lean condition from a clogged fuel system or preignition due to low octane can destroy a 2 stroke outboard easily.

 

[sho3boater]

Re: Fuel Left in Motor ???

This guy has most of the info, though he states the octane does not change how it burns just knock resistance. I have read recent tests showing more carbon build up from high octane fuel as well as actually getting less power from it if the engine is optimized for the lower octane fuel.

http://www.ar15.com/forums/topic.html?b=1&f=5&t=908990

No, I just found it in google lol.

 

[Silvertip]

Re: Fuel Left in Motor ???

My personal John Deere mower is probably older than you are and just happens to have a Kawaski OHV motor on it. I live in Minnesota, we've used E10 for well over a decade, and that particular engine (as do my chain saws (Stihl, Poulan, and Craftsman, weed whips, Kioritz powered leaf blower and my 21 HP Tractor all sit for six months each winter. On the flip side, my 12 HP snowblower sits longer than that and none of these engines give me any grief. The oldest is a 1978 Craftsman chain saw and the only fuel issue that has presented is the ethanol caused the fuel line in the tank to deterioriate. Treat the fuel and park it. It's standard procedure up here. As was pointed out, higher octane prevents detonation. Hardly a problem on small engines. The fuel doesn't make a bigger "bang" - it prevents the bang from occuring too soon.

 

[sho3boater]

Re: Fuel Left in Motor ???

The one I put premium in was a 60s V8 I/O with a Holley carb, it would suck in the carb gaskets if I let the carb run dry. I had to move those Kaws back in the 90s and we didn't have ethanol then. You can believe what you want, but they pulled hard so I'll not forget them.

 

[Lion hunter]

Re: Fuel Left in Motor ???

The quotes are from the web link you provided.

"Octane is simply the fuels ability to resist knock (detonation)"

I agree with it. Detonation and ignition are the same. The abilty to resist detonation is the same as retarding ignition.

"For storage, buy the higher octane fuel that is ethanol free"

Sort of what I said as far as the ethanol free. Although as far as I know ethanol free only comes in 91 octane if you can find it.

"For long term storage it would be better to buy the higher octane fuel since in theory it should take longer to reach a low enough octane rating to be insufficient."

What he is saying makes sense. But whether you start with 87 or 91 the fuel is going to deteriorate at the same rate. The difference being that the 87 will now be down in the 80's and the 91 will be 86. But the harmful gums and varnish exist with both fuels.

Now from my personal experience. With a Stihl chainsaw, Honda push mower, Kawasaki KZ1000, and a Echo trimmer. All of these sit with last years fuel from November until the end of April. None of them have ever gave me
any problem starting. Does fuel deteriorate and go bad. Yes, I have seen the evidence and seen how ethanol seperates. Should you use a fuel stabilizer when storing. I think so and do when I remember but when I have forgot there have been no ill effects that I know of. I live in Idaho, and Silvertip in Minnesota so maybe the cold preserves better, keeps the fuel from volitizing or something. On that I have no idea. But the idea makes sense that hotter weather would speed the oxidation of fuel.

By the way that was a very informative read you provided shoboat. I'll have to add that to the faves. Now I digress, we have really strayed from the OP's question. No I do not run the fuel from the carbs.

 

[Silvertip]

Re: Fuel Left in Motor ???

Better check the pumps where you buy 91 octane (or even 89 octane). You may be surprised that it too contains ethanol. Some states don't even require the pumps to have the ethanol label so you may be using E10 and not even know it.

 

[Lion hunter]

Re: Fuel Left in Motor ???

Your right most do have ethanol. There are 2 stations that have 91 with no ethanol. Being that I have no way to really check it , and I don't buy it, I'd have to take the owners word for it.