Run the outboard empty every time?

[saillr]

In the newer 4 stroke engines the tiny needle valve orifices are more sensitive to crud.
I have found that using ethanol gas mix does cause problems in the carburetor when left for a period. The ethanol attracts water and the water will cause corrosion especially on the brass parts in the carb such as the float needle valve. Green crud really messes things up. Since using ethanol free gas it starts better, runs better and doesn't cause crud in the carb.

[moctrams]

I meant to say Ethanol FREE

[goodoldvega]

This goes back to old 2 - stroke engines, where the fuel would evaporate while the engine was in storage, just leaving the 2 - stroke oil in the carburretor. So when starting up again after storage, there would be rather too much oil and they wouldn't run........ Some of these old engines, like British Seagull, ran fuel / oil ratios around 10:1, so they left a lot of oil behind after the petrol evaporated!

[Cpt Pat]

Originally Posted by saillr

In the newer 4 stroke engines the tiny needle valve orifices are more sensitive to crud.
I have found that using ethanol gas mix does cause problems in the carburetor when left for a period. The ethanol attracts water and the water will cause corrosion especially on the brass parts in the carb such as the float needle valve. Green crud really messes things up. Since using ethanol free gas it starts better, runs better and doesn't cause crud in the carb.

You are right: ethanol is water miscible and forms a homogeneous solution with water. In other words, you can't separate it out like you can with pure gasoline and water (water is heavier than gasoline and readily separates by gravity).

I have an airport nearby with self-serve pumps. I ran my engine experimentally on 100LL: 100 octane "low lead" aviation gas. I had to continually scrape the lead fouling off the spark plug gap (if you're old enough, you'll remember lead fouling).

I'm not sure which is worse.

I do know that breathing gas fumes with atomized lead when motoring downwind isn't good for my brain. Anyone over 40 is permanently lead poisoned from leaded gas. I don't need to add to that.

[thinwater]

Still no factory advice. Does it not seem that if draining every time were vital to avoiding problems under warranty, it would be in the manual? Heck, there's tons of detailed service advice we don't follow, so why is something so critical, and obviously so well known, glaringly missing? Heck, the engineers all have small gas engines at home. Many are boaters. Do we actually think they all just... missed this? I don't think they did.


E10 will dissolve about 0.6% water, depending on temperature (less when cold). If there is more water than that, it separates, though rather slowly, because the aqueous (lower) phase is 80-90% ethanol.

The cause of the corrosion is that gasoline/ethanol/water mixtures conduct small amount of electricity, accelerating galvanic corrosion. The "crud" you are seeing is aluminum hydroxide gel in water, not gum.

[sailorboy1]

Nothing in my Tohatsu manual says to run it dry. I just got a Honda EU2200i and didn't see anything in it that says to.

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).

[wsmurdoch]

I have six carbureted outboards 1.5 to 40 hp, 1967 to 2017, both 2 and 4 cycle (ask my wife about it). I don't think any recommend running the carb dry or draining the bowl after each use. Long term storage or water submergence is different. I can find a reference to draining the fuel then.

I have been told that a 2-cycle engine will run on the EtOH/H2O phase in the bottom of the fuel tank and that with little dissolved oil in that phase that it can be disastrous due to a lack of lubrication. But, I have never seen that said in writing by a competent authority.

Bill

[Dave_S]

Sorry no links but

A long long time ago racing 2 stroke go karts, we used to run engines with very close tolerances for best performance and it is likely you would seize the piston to the cylinder wall if you let it run out of fuel.

They would seize because the piston expands faster than the cylinder it is in. When the mixture leans out the charge burns hotter and the piston grows faster than the cylinder and it binds in the bore which galls and then welds in place.

It is much less likely to happen at idle and much less likely to happen with engines with bigger clearances. If the engine doesn't seize it is unlikely to have sustained any harm.

I doubt it is a problem, I do it every time with my wipper snipper (weed wacker) and used to when my mower and outboards were 2 stroke.

[CarlF]

Thinwater, thanks for the "aluminum hydroxide" answer for ethanol. I've never seen that before. It would explain why carb cleaners are useless once the corrosion is there. It's amazing how much mis-information is out there about ethanol fouling. I still have friends who swear by the old carb cleaners.

How do keep E10 from fouling a 4 cycle outboard? Preferred additive? Other tips?

My 15HP Honda 4 cycle dinghy outboard is very sensitive to ethanol fouling. I agree running the fuel out doesn't work. I carry a spare carburetor as an ultrasonic cleaning by a mechanic costs almost as much and doesn't alway last. I have no problem when I'm south where ethanol free gas is easy to get but in New England it's all E10 - unless I buy the small engine gas at $25/gallon.

[Mirage35]

More anecdotes (no knowledge to support anything):

I tend to run the outboard dry each time, just because this motor gave us a hard time when we first had it. But since I had it professionally tuned and cleaned it's been much better generally. And I don't do this with any other small engines I own, some of which operate in worse conditions.

So, yes, I do it but, on reflection, suspect I don't need to.

[thinwater]

Originally Posted by wsmurdoch

...I have been told that a 2-cycle engine will run on the EtOH/H2O phase in the bottom of the fuel tank and that with little dissolved oil in that phase that it can be disastrous due to a lack of lubrication. But, I have never seen that said in writing by a competent authority.

Bill

I have been told by engineers well-up at a mjor outboard manufacturer that they have seen engines damamged that way. Yes, it is true that the separated phase contains no oil.

[thinwater]

Originally Posted by CarlF

Thinwater, thanks for the "aluminum hydroxide" answer for ethanol. I've never seen that before. It would explain why carb cleaners are useless once the corrosion is there. It's amazing how much mis-information is out there about ethanol fouling. I still have friends who swear by the old carb cleaners.

How do keep E10 from fouling a 4 cycle outboard? Preferred additive? Other tips?

My 15HP Honda 4 cycle dinghy outboard is very sensitive to ethanol fouling. I agree running the fuel out doesn't work. I carry a spare carburetor as an ultrasonic cleaning by a mechanic costs almost as much and doesn't alway last. I have no problem when I'm south where ethanol free gas is easy to get but in New England it's all E10 - unless I buy the small engine gas at $25/gallon.

Yup, don't expect solvent-based carb cleaners to remove metallic corrosion products. A good jet blast, however, still works.


I've published a number of articles and I plan another series of tests this fall, for all the new formulas. There is a new draft testing method warmed up and ready to go.


My opinions and practices are these:

• Keep the fuel bone dry. Run as often as possible, at least monthly even in the off season. Keep portable tanks covered if possible, to keep the sun off and to keep rain out. Close the vent when not actually running (portable) or use a silica gel vent filter (installed).
• Use an additive proven to inhibit aluminum corrosion. Merc Quickstore,Seafoam, and Biobor EB (my favorite) have done very well in repeated testing.

Those are the two keys, IMO.

[a64pilot]

Originally Posted by thinwater

Still no factory advice. Does it not seem that if draining every time were vital to avoiding problems under warranty, it would be in the manual? Heck, there's tons of detailed service advice we don't follow, so why is something so critical, and obviously so well known, glaringly missing? Heck, the engineers all have small gas engines at home. Many are boaters. Do we actually think they all just... missed this? I don't think they did.


E10 will dissolve about 0.6% water, depending on temperature (less when cold). If there is more water than that, it separates, though rather slowly, because the aqueous (lower) phase is 80-90% ethanol.

The cause of the corrosion is that gasoline/ethanol/water mixtures conduct small amount of electricity, accelerating galvanic corrosion. The "crud" you are seeing is aluminum hydroxide gel in water, not gum.

Gummed up carburetors isn’t a warrantable event, if your Dealer fixed it for you under warranty, it’s likely that he “ate” that time, I can’t image the factory paying him to clean a carburetor.

You not going to hurt any engine from going lean at idle, yes all engines, especially high performance two strokes run excessively rich at full throttle, fuel is used as a coolant and it helps prevent detonation too, so going lean at a full throttle run and leaving it lean could hurt it, but running out of gas goes lean for such a short time, it’s not going to hurt anything.

I can remember my Father disconnecting our Mercury “tower of power” in line 6 cyl two stroke to run it out of gas, and he would only burn Amaco “white” gas, remember that stuff?
I figure it can’t hurt, but my outboard is fuel injected and seems impervious to fuel, I’ve left fuel in it for five years now in the off season, no effect at all.
Fuel injection is the way of the future in my opinion, and four strokes.

[David Sandowich]

by eliminating ethanol fuel ( if you can ) i have found solves many of these issues that have plagued me for years with my small 2 and 4 strokes. As you all know they now sell it in the box stores as well as hardware stores. I have a small airport near me and use aviation gas. Since this switch ... not a problem. Fixed the issues with the weedwacker and chain saw also

[Shrew]

I leave the fuel in if I'm using it the next day. I run it dry if I'm hauling the dinghy or if it will sit for more than a few days. I'm honestly not sure I care terribly much. A carb rebuild kit is typically 60% percent of a new carb. The new carb is typically under $100 and worst case scenario, can go at least 5 years between new carbs. Replacement takes about 15 minutes which is significantly faster and easier than cleaning and rebuilding.

For the extra $40-$50 every 5+ years........I've already lost interest. LOL!!!