Run the outboard empty every time?

[thinwater]

Yes, this is the factory advice for seasonal storage. Yes, I know the typical mechanic and forum wisdom. But several years ago I spoke with a factory engineer that told me they had removed the advise to drain the gas after each outing from the manuals because the practice actually increased fouling (the carbs are far more likely to actually dry if they are mostly drained).


Does anyone have an actual cut-and-paste factory manual quote advising to drain the outboard after every use? I'm sure folks would like to see it. I have not found such advice in writing.

[Calif.Ted]

Not every use but for Transporting/storage

2. Drain the fuel 1. Turn the fuel valve lever off. 2. Remove the fuel filler cap and drain the gasoline from the fuel tank in- to a suitable container. 3. Turn the fuel valve lever on, loosen the carburetor drain screw , and drain the gasoline into a suitable container. 4. After draining, retighten the drain screw. 5. Make sure the fuel cap vent knob is turned to OFF.

https://cdn.powerequipment.honda.com...s/31ZV0610.pdf

Honda 2hp page 35 of manual

[model 10]

I disconnect the fuel hose and let the engine quit. The engine starts almost as normal 6 months later.

[contrail]

Originally Posted by Ecos

I disconnect the fuel hose and let the engine quit. The engine starts almost as normal 6 months later.

That's pretty much what I do at the end of each charter, unless I am going back out in less than a week, with the same results. And if I don't, then the engine is almost unfailingly hard to start and gets increasingly so until I change the plugs, clean the carb, or both. Learned the hard way, over fifteen otherwise delightful years with the same engine.



As for draining absolutely everything, I would bet that it's a lawyer's way to mitigate risk of some stray fuel exploding, rather than protecting the carb.

[Calif.Ted]

I just shut-off the fuel valve and let it run dry if it's going to sit a week or more also, I believe my Honda 2hp must be almost 15 and on the original plug.

[Don C L]

I have no cut and paste advice but I guess I can imagine what the mechanic is saying. Is this for 2 or 4 stroke or does it matter? On my (30 year old... yikes!) 2 stroke 8hp I remove the line and run the engine till it quits if I am not going to be using it in the next day or so. My old engine runs fine. Still has good compression too.

[Sojourner]

I run my yamaha 4 stroke dry if I'm not gonna be using it for a week or more. It starts easier somehow. Did the same on my 2 stroke mercury, same thing. With the yammie, seeing as how easy she is to flush onboard (they have a garden-hose type adapter that you can plug into your freshwater deck shower), I give her a quick freshwater flush every time she comes out of the water. or if she's been in the water a week.

[GordMay]

Originally Posted by Calif.Ted

Not every use but for Transporting/storage
https://cdn.powerequipment.honda.com...s/31ZV0610.pdf
Honda 2hp page 35 of manual

Originally Posted by thinwater

...r seasonal storage. Yes, I know the typical mechanic and forum wisdom. But several years ago I spoke with a factory engineer that told me they had removed the advise to drain the gas after each outing from the manuals because the practice actually increased fouling ...

And from a manual dated 1989.

[thinwater]

The problem with anecdotal information ("I did this and it works great") is that does NOT tell us if something else would have worked better.


I have not drained a carb or let a motor run dry in the 15 years since I began researching fuel and I have not had a single carb problem either (I have owned 4-5 older engine through the period). I've kept the fuel dry and used a corrosion inhibitor.


Mechanics can be knowledgeable about fixing motors, but they don't really know how motors are used or what caused the problems, other than their own. Like us, they go by rumor, and I've heard some astonishingly poor advise from mechanics.



---


Thus, I'm just trying to see what the manuals say. Then I will call factories. In fact, I've been closely involved with the ASTM fuels committee for many years and have already spoken with a few of the guys.

[a64pilot]

Originally Posted by thinwater

I've heard some astonishingly poor advise from mechanics.

Even sometimes in factory manuals, especially if the manufacturer uses an item in their machine, that they purchase and actually know little about.
It seems to get worse with small manufacturers.
They way manuals come into existence is interesting. I have written aircraft manuals, that were of course FAA approved, by myself.
Think maybe some of my beliefs made it into the manuals?
But it must be a fact, it’s not only the factory manual, it’s FAA approved

[moctrams]

I use Ethanol gasoline in all of my small engines and I turn the fuel off, or empty tank in my Johnson 2hp outboard when I’m finished. When I put them away for the winter I “fog” them. They start right up in the spring. I find 10% Ethanol fuel fouls my spark plugs. What will it be like when it’s 15%?????

[LeeV]

Originally Posted by Ecos

I disconnect the fuel hose and let the engine quit. The engine starts almost as normal 6 months later.

[wrwakefield]

I've never drained any carborated engines, and have had few problems over the years. This includes snowblowers, ATVs, snowmachines, outboard engines, etc. [This sampling includes 8+ carborators- several of which were stored outdoors where in winter that could mean -40° [either scale] and colder... and still fired right up when needed...

I always put the prescribed amount of Seafoam in all gasoline when fresh, and keep the tanks full and moisture free. [Fuel is filtered on the way to the engines. ]

One factor that may mitigate potential fouling issues is what I am reporting all occurred between 56 and 66°N; and to my knowledge, we still don't have to deal with ethanol in our gasoline up here... [Alaska still has an exemption last I knew...]

What does the Yamaha 15D [2 stroke] outboard manual advise? Use a fuel preservative... [screenshot appended below...]

In case this is useful.

Cheers! Bill

[Cpt Pat]

Originally Posted by Ecos

I disconnect the fuel hose and let the engine quit. The engine starts almost as normal 6 months later.

I do the same - with the same result.

My 2017 Nissan manual instructs users to run the engine dry, as you describe. This practice also gives time for a gradual cool-down at idle, which reduces thermal shock.

Running an engine critically lean to the point of engine shutdown is a standard operating procedure for piston aircraft engines (both carbureted and fuel-injected). Just shutting off the ignition with atomized fuel still present in the intake manifold of a hot engine invites a few cycles of dieseling, which is murder for a gasoline engine (and potential homicide if the engine later swings the propeller around when the last bit of fuel in a cylinder later cooks off). Out on the water, I at least provide a few minutes of cool-down at idle in neutral before using the magneto cut-off, which I avoid using whenever possible. It takes only a few seconds to reprime the carb when I restart.

On my previous boat that had an inboard gas engine, I installed a solenoid valve upstream of the carb that I'd use for shutting down the engine. It took a second longer to start, while the fuel pump refilled the carb reservoir, but I never had a carb fouling issue.

[northwestsailor]

I have switched over to synthetic fuel for my 2.5hp Honda. No problems since switching and starts every time. Honda dealer and mechanic suggested this and so far best advice I have received. I tried the run out method and it worked for a while then without warning could not the **** thing started to save my life. Synthetic does not go stale. Not expensive but available for less at Home Depot.