Run the outboard empty every time?

[Cpt Pat]

Originally Posted by sailorboy1

Personally I don't see why running dry would be a plus for a problem that is about corrosion (outboards wouldn't run dry on separated water).

Leaving gasoline in the carb reservoir ("bowl") causes it to eventually evaporate there. (The reservoir isn't air tight.) Each time that happens, a new layer of residue is laid down. It forms a plaque of "gum" that doesn't fully dissolve the next time the reservoir is refilled. Eventually, this gum buildup plugs the gasoline injection jet to the venturi (carb "throat").


The water contamination issue with ethanol is a separate issue that causes rough running and an effective reduction of the fuel's equivalent octane.

[jmschmidt]

I too previously unplugged the fuel line and let the motor run dry. And then I had a tune-up done by this old wharf rat of an outboard motor specialist who lived by the marine and he told me not to do that because it removes any lubricating quality from the fuel left inside and the reason offered by the factory engineer you spoke to.

The old guy was the most knowledgeable, fast and inexpensive of any outboard mechanic I have every used in the last fifty years.

[roverhi]

Not an outboard but have a Honda Commerical lawn mower that I've owned for 25 years. Because of weather patterns it gets used every other week or three for half the year and once or twice in the other half. Have always used alcohol free gas and turned off the fuel and let run dry every time used. It has always started on first or second pull During all those 25 years. The engine is going to outlast the Mower body surround which has been welded often from hitting rocks.

[Cpt Pat]

Originally Posted by jmschmidt

... he told me not to do that because it removes any lubricating quality from the fuel left inside and the reason offered by the factory engineer you spoke to.

I assume that is a 2-stroke engine. Otherwise, you shouldn't have any oil in the fuel. Gasoline alone has almost no lubricating properties.

Diesel fuel, on the other hand, does provide some lubrication, which is one reason why those engines wear much more slowly.

[Shrew]

Originally Posted by jmschmidt

I too previously unplugged the fuel line and let the motor run dry. And then I had a tune-up done by this old wharf rat of an outboard motor specialist who lived by the marine and he told me not to do that because it removes any lubricating quality from the fuel left inside and the reason offered by the factory engineer you spoke to.

I'd be curious whether this is rooted in 2stroke technology where there is oil mixed in the fuel. I also wonder whether this theory is rooted in pre-ethanol thinking as well.

Which is the lesser of two evils? Lack of lubrication or the build-up of gunk and ethanol-related issues.

[Chotu]

I just run ethanol free fuel with stabilizer in it. Then I don’t worry about that stuff. However, running ethanol or not using stabilizer has definitely created carb problems for me in the past.

[a64pilot]

Even if a two stroke running it out of gas isn’t going to hurt it at all from a lubrication perspective.
The oil injection engines would run as lean or leaner than 200 to 1 at low throttle. A two stroke needs very little lubrications at low power / RPM.

Plus guys you have to realize the time the engine is running lean is only a few seconds, right before it shuts off, it’s not running lean the second you disconnect

[markbarendt]

“Aside from evaporation, "[gasoline] is like wine — once you take it out of the bottle, it starts going bad. It starts oxidizing away," Stanley said.

As some of the hydrocarbons in the gasoline evaporate, other hydrocarbons react with the oxygen in the air, Speight said. The gasoline then begins to form solids called gum.”
"[O]nce [the bad gasoline] gets into the pipeline, that gum may separate out ... and maybe [it will] not block the gas line fully, but maybe [it will] start to block it," Speight said.

"You can almost say that gumming of the gas lines is like atherosclerosis," he added, “
https://www.livescience.com/58117-do...ne-go-bad.html

[DeepFrz]

Amazing how few of the respondents even understood the question but just blurted out an opinion on something that was not asked.

[markbarendt]

Originally Posted by DeepFrz

Amazing how few of the respondents even understood the question but just blurted out an opinion on something that was not asked.

Giggle, really, your surprised a conversation strayed? C’mon?

[Don C L]

Originally Posted by DeepFrz

Amazing how few of the respondents even understood the question but just blurted out an opinion on something that was not asked.

Well... I woulda if I coulda, but who keeps a 30 year old manual? Ok, well, maybe I do have it around somewhere....

[thinwater]

Originally Posted by Don C L

Well... I woulda if I coulda, but who keeps a 30 year old manual? Ok, well, maybe I do have it around somewhere....

Search on-line (since we are all on-line).


I threw down the gauntlet regarding any written factory advice. That's all. It appears the only written factory advice, for all brands, is to drain for seasonal storage. I have also spoken with factory engineers.


The other thing is that when to drain does not have a black and white answer. All will agree that 3-6 month storage justifies draining. All will agree that a lunch stop at dockside watering hole does not; your just going to wear out fittings for nothing. You actually increase gum formation, because you have caused the carb to dry when it otherwise would have stayed wet. Somewhere in between 30 minutes and 3 months there is a threshold where draining is better.


Discussing best practices in a forum, on the other hand, leads to an "anchor thread." Fun, but wandering.


Some time ago I did a series of accelerated aging tests (heat and air) for publication, following ASTM methods, intended to simulate years in a tank or months in a carb. You would be amazed at how difficulty it is to make gasoline oxidize and form gum if treated with a modern additive. It is all but impossible, just as it comes from the pump. The chemistry has improved. Has no one noticed that gasoline has become water-white over the years? Stability standards have improved and we are no longer seeing gum, we are seeing corrosion and corrosion products. Carbs arn't full of dark, gummy stuff, we see white-green puffy deposits of aluminum hydroxide gel. But old "experience" dies slow.

[wsmurdoch]

Exxon sys... Does gasoline have an expiration date and how long can it be stored?
In general, gasoline should be used within a month of purchase. When the engine will not be used for an extended period of time, it’s best to drain the fuel tank and then run the engine until it stalls. If you choose to store gasoline and follow proper storage guidelines, the gasoline can be expected to remain of good quality for at least six months.

https://www.exxon.com/en/gasoline-safety-storage

Bill

[Matsubob]

Gasoline these days has so many additives and prohibitors and ehnancers that fuel goes stale and won't ignite. Especially if it is a small engine that is carbureted, the primary (as in "idle") circuit in the carburetor has such a tiny orifice that any small amount of corrosion can clog it and the engine will then refuse to idle. This is true for small bike engines, chainsaws, cnowblowers, weed cutters, as well. It is the size of the engine and the tiny orifices that get clogged wasily, in addition to gasoline going stale. The additives in gasoline often corrode the aluminum casting of the carburetor, either causing varnishes to form or actual corrosion of the aluminum fuel bowl.
Fuel stabilizers tend to help delay the aging process so that may be the way to go. It is just easy to forget, and almost as easy to just run the thing dry on the last use, so it will start right up the next time you use it.
A few months won't make a big difference but if the engine is out of use over a winter, it is just a good idea to run it dry.

[Seadaddler]

I don’t run my outboard dry except when I go up north in summer and last year
I was going crazy getting boat canvas stripped and any portable electronics and
any equipment I think is good idea to remove from boat and also was getting RV
packed and ready for 3 month trip.
But any way I never got chance to run my outboard dry and when I did return 3 months later and started it up it started no problem,I do use ethanol free gas and regularly add Sea Foam to the gas and it always runs great.
Nick