Run gas out of 4 stroke

[tommybe1]

Are there any negatives to running the gas out of a 4 stroke when its going to sit for a few months with ethanol gas in it?

[Harper]

No problems that I know of. I ran my DF150 out of gas once, not on purpose. But other than a longer crank on the first restart, nothing happened to the motor. I don't do it intentionally, as you're suggesting, but I understand your concern. I don't use ethanol-laced gasoline.

[Moonlighter]

Not recommended, or necessary.

The engines are designed to deal with up to 10% ethanol fuel. Its not like the old days where fuel with oil in it sat in carbys and gummed them up.

Add some fuel stabiliser to the tank, run the engine for 15 minutes to get the treated fuel thru the system. Done.

Electronic fuel pumps on efi engines can be damaged by running them dry.

[tommybe1]

Thanks ML, Will do, I seem to have problems even with addiing a stabilizer, sometimes sits for 3 months without getting used, still not sure if thats all my problem, but did seem to help when run on a seperate gas can with fresh gas..

[Murray]

On my 2009 DF90A there is a bolt at the bottom of the fuel rail, once that’s released the fuel should drain out both directions if the inlet line is disconnected. Drain the VST if you want to evacuate all the fuel from the system. I have realized that once you add stabilizer to the fuel tank it takes longer than the owners manual states to completely exchange the old fuel with the fresh stabilized fuel. When I winterize my fuel system I start long before I pull the boat out of the water, I give it a couple of good runs prior to pulling it off the lake.

[Murray]

One question. If you run the pump dry what is providing cooling and lubrication to the fuel pump?

[Harper]

The reason that I would not really be concerned about running the outboard out of fuel, is that unless the ECM senses that the engine is actually turning, it will not send any power to the high pressure pump. I really doubt that the pump would run long enough after shutdown or stall to do any damage to it at all. The pump should stop running immediately when the engine stops. When the VST empties, immediately the pressure in the fuel rail will drop to the point that the engine will stop, and the ECM will shut the pump down.

[Moonlighter]

Dont forget the LP fuel pump. Its the one that you hear humming as soon as the key goes to the on position. As long as the key is on, that pump will be working or at least cycling.

It would be trying to suck fuel when there is none there, so I think you would be putting more stress on it than necessary. Would that damage it? Maybe, if repeated enough?

I want to know what the problem is that the solution is to disconnect the fuel line and run the engine’s fuel system dry. Unless there is a problem that this solution fits, then why go there?

Or - Is it just a practice left over from the 2-stroke days?

[Harper]

I really don't know that it's a solution to anything, or that it's even necessary. My only observation is that it isn't likely to hurt anything. My LP fuel pump is a cam driven diaphragm pump. Only electric is the HP pump. DF150. When I turn on the key, it's the HP pump going through a timed duty cycle to pressurize the fuel rail.
'
Once the HP pump has run it's cycle, it will stop, pressure or no pressure. And since you ran out of gas, that's when you're going to need to squeeze that primer bulb before cranking to get some fuel up to the LP pump so it can get fuel to the VST relatively quickly. It will take a bit longer than normal to start the motor, of course.

[Harper]

What we really need to know is which motor tommybe1 is talking about. The larger Suzukis, the V-6s, I believe have an electric LP fuel pump. But i was under the impression that all the straight 4s had the same mechanical LP pump as my DF150.

[tommybe1]

Its a DF50, plan on taking it out tommorow, see how its running, my initial thought was the ethanol fuel was causing a problem when sitting for a couple of months even with stabil added.

[Murray]

I wouldn’t think a couple of months of stabilized fuel would cause any issues assuming you mixed to the manufacturer’s specifications and the fuel was fresh the 2 months ago.

[tommybe1]

I ran it on a lake yesterday and it was cutting out bad, this was with new gas, as I had emptied out the old and ran the motor out of gas before hand. I switched to a gas gan with a gallon of gas and a can of sea foam and ran it almost out. After that it ran good except for an occasional stutter at 4000 rpm, so it seemed as if something was clogged up. maybe not the whole problem but sure helped.

[Murray]

Check Seafoam’s website, if memory serves they recommend a 50/50 mix of Seafoam to fuel, You can buy Seafoam in a US gallon container. A slight stutter could be a spark plug acting up.