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6HP outboard engine sputtering

Jun 8, 2004
8,885
-na -NA Anywhere USA
I think he may not have cleaned out that carb jets enough. for the record, I was the first recorded dealer telling everyone many years ago about the issues with corn syrup (ethanol) or corn crap clogging the jets in these small carbs. Best advice is to buy ethanol gas and let the engine run out of fuel every time. Many who do this report back no issues with engiens for years. Of course it could be other issues but the above advice given and to what I said should always be adhered to.
 

jviss

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Feb 5, 2004
4,627
Tartan 3800 Westport, MA
Best advice is to buy ethanol gas
Did you mean to write "ethanol-free gas?"

You can get that, of course. It's super expensive in cans at the outdoor equipment places. Most cost-effective is CAM 10 100 octane racing fuel at about $10/gal. Sunoco Optima is available in 5 gallon pails for $95.
 
Jun 8, 2004
8,885
-na -NA Anywhere USA
as long as ethanol free I do not care where I get it. I was the first small boat dealer to figure this out and started advising other sailboat dealers quickly as it nearly cost me a sale. Sure you can add additives but ethanol free is better. If anyone is considering cost, well think twice on this.
 

jviss

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Feb 5, 2004
4,627
Tartan 3800 Westport, MA
the issues with corn syrup (ethanol) or corn crap clogging the jets in these small carbs.
I hope you are saying this tongue-in-cheek. You realize, of course, that ethanol made from corn is indistinguishable from ethanol made from anything else.
The problem isn't corn residue or "corn syrup" clogging things. It's that ethanol absorbs water, and that it attacks seals and gaskets made of certain materials, as well as other parts. It leaches-out constituents of many plastics. Neoprene O-rings will swell, vinyl-like tubing will shrink, and so on. Ruined two Merc gas tank pick up assemblies on me. The water causes problems, too.
 

Ross S

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Oct 20, 2011
120
Precision 21 Great Sacandaga Lake
I hope you are saying this tongue-in-cheek. You realize, of course, that ethanol made from corn is indistinguishable from ethanol made from anything else.
The problem isn't corn residue or "corn syrup" clogging things. It's that ethanol absorbs water, and that it attacks seals and gaskets made of certain materials, as well as other parts. It leaches-out constituents of many plastics. Neoprene O-rings will swell, vinyl-like tubing will shrink, and so on. Ruined two Merc gas tank pick up assemblies on me. The water causes problems, too.
I suspect he's alluding to the fact that ethanol gas wasn't introduced for any reason other than to give US farmers an additional market to sell their corn into. By any rational measure ethanol gas makes no sense. It's more expensive, less efficient and wreaks havoc on smaller or seldom used motors.

That said, ethanol is ethanol regardless of where it comes from and it doesn't belong in gasoline.
 
Oct 22, 2014
16,107
CAL 35 Cruiser moored EVERETT WA
And it has not done to well for the corn crop marketing. Now it is costing more to feed us than before. All that corn going to fuel rather than to feed lots. Then you have the cost of oil wavering. It is a viscous circle.
 

Ross S

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Oct 20, 2011
120
Precision 21 Great Sacandaga Lake
And it has not done to well for the corn crop marketing. Now it is costing more to feed us than before. All that corn going to fuel rather than to feed lots. Then you have the cost of oil wavering. It is a viscous circle.
It's a great example of the law of unintended consequences.
 
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Adam D

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Sep 8, 2017
12
Catalina 22 Harrison Lake
Blowing it out is often not enough. Soak it in a bucket of actual carb cleaner for 4 hours. After that use spray on the jets.
I did clean it as well. Still didn't work. changed the spark plug and that didn't change anything. The old plug had a black tip though. Too rich I guess. I would’ve pulled out the plug before but I didn’t have the tools on board (which is dumb and I do now have the right socket in my on board tool kit from now on). Now I’m thinking I will just adjust the screw for air tomorrow. Will tinker with it and see what happens.
 
Last edited:
May 17, 2004
3,472
Beneteau Oceanis 37 LE Havre de Grace
The old plug had a black tip though. Too rich I guess.
Too rich is inconsistent with the fact that you said the engine runs better half choked. Unfortunately I'm still in the camp of it being a carb issue, which I could imagine would be pretty frustrating after cleaning it all. You could check in the carb to see if it has any eubber seals. Sometimes they swell from ethanol. Had a problem once where the seal around the needle valve that lets fuel into the bowl swelled and starved the engine.
 
Jan 27, 2008
3,008
ODay 35 Beaufort, NC
Could the tank have gunk in it restricting the fuel pickup? Is the squeeze bulb in the right direction? Is the squeeze bulb mounted vertically? Is the vent on the tank open?
 
Nov 6, 2006
9,225
Hunter 34 Mandeville Louisiana
Check your quick disconnects in the fuel line.. the one at the motor and the one at the tank. a very small air leak either on the hose connection or a bad o-ring in the fitting can cause sputtering as you describe..
 

Ross S

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Oct 20, 2011
120
Precision 21 Great Sacandaga Lake
I did clean it as well. Still didn't work. changed the spark plug and that didn't change anything. The old plug had a black tip though. Too rich I guess. I would’ve pulled out the plug before but I didn’t have the tools on board (which is dumb and I do now have the right socket in my on board tool kit from now on). Now I’m thinking I will just adjust the screw for air tomorrow. Will tinker with it and see what happens.
If you're going to adjust the mixture screw, then first screw it in until it bottoms out while counting the turns. That way you can return it to where you started and at least have that starting point to go back to. Personally, I've only ever had very mixed success adjusting mixture "by ear". For most newer engines, the mixture is not considered adjustable and has a plug installed over the mixture screw. But you can remove the plug and adjust it if you like.
 
Aug 22, 2017
1,608
Hunter 26.5 West Palm Beach
The original symptoms are consistent with either fuel starvation from one of multiple delivery circuits in the carburetor being clogged or else a timing/ignition problem. If pulling the choke out part way made the problem go away, then it’s most likely a fuel problem.

Almost all carbs have more than one fuel circuit. Each circuit handles a different RPM range. Most circuits have removable jets. The jets are usually what gets clogged from crap in the fuel first, but small passages can also get clogged. The best way I have found to clean jets (if they are not stuck in place from old age) is to remove them, soak them in carb cleaner until the crud softens, then run properly sized nylon guitar strings through them to scrub out the crud. The passages behind the jets can be tougher to clean if the crud got that far back.

If you ran partially choked, then the spark plug will get dark from when you ran on a circuit that was operating properly. Partial choking covers for the lean condition on the clogged circuit, but makes the other circuits run rich.

Modern carbs are jetted as lean as possible while still being able to run, so they are more sensitive to very small restrictions compared to older engines. Adjusting the jetting slightly richer will usually make the engine more user friendly at the expense of increasing emissions to a level that is probably outside of legal limits.

Ethanol gas is a good choice if you are going to run the tank just about dry, then put some ethanol free behind it before you shut the motor down. The ethanol gas has slightly better solvency properties than the ethanol free gas & actually helps to keep the fuel system clean when it goes through, but ethanol gas is not your friend when it sits in a tank or a carb for a long time, especially in humid environments. The solvency related issues have already been mentioned. The other big issue is that ethanol sucks moisture out of the air, binds with it, then forms a noncombustible goo that sits on the bottom of your tank or the bottom of your float bowl & plugs things up. Once the goo is formed, the additives can’t break it down. They can only prevent it from forming if they are added when the fuel is fresh. The additives buy you some time (months), but they don’t make the fuel last forever & they don't prevent the ethanol from attacking older rubber parts that were made before ethanol was a normal ingredient in motor fuels.

Ethanol free gas is available at some gas stations in most states. A pretty good listing of availability by state can be found here - https://www.pure-gas.org/
 
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Jun 8, 2004
8,885
-na -NA Anywhere USA
Ever since the intro of ethanol gas the first thing I look at are the jets on the carb and generally cleaning solves the problem. Cover time it has also wrecked havoc on seals and gaskets. I think the gasket issues has been addressed with new engin and replacement gaskets. I loaned my chain saw out last month to be returned not running when the fellow used ethanol gas. Cleaned the carb and removed the fuel for new ethanol free gas. Runs like a charm. Will not lend my chain saw to him again
 

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
Modern outboards don’t have ‘air screws’. You are left with adjusting the idle speed, and throttle setting. All the carb jets are fixed. Simple soaking in carb cleaner is not sufficient, you need to either give the carb a day in an utrasonic cleaner with carb cleaner or do a careful hand cleaning. You are fouling your spark plugs by using your choke to get enough fuel into the engine. Also loading the engine with carbon. Fix it right.
 

jviss

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Feb 5, 2004
4,627
Tartan 3800 Westport, MA
Modern outboards don’t have ‘air screws’.
Are you sure? Also, please define "modern."

I have several outboards made within the last 20 or so years, and all of them have air screws in the carb.

Thanks to the EPA, many carburetors have the air screw set at the factory, and then obscured, with a plastic or metal cap, to prevent owners from adjusting them. The cap usually must be destroyed to access the screw. The idea is that only a service center can access this, and they are then required to re-cap it when done. These engines are set to run fairly lean to satisfy EPA emissions requirements. This is so on most chainsaws, blowers, weed whackers, and yes, outboards.

Here's a video that shows how to remove the cap:
 

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
Here is Adam’s carb, where is the air screw? Hint: There is none. They went away because the manufacturers didn’t want you being able to violate their exhaust gas certifications. Carbs are a dying concept for lots of good reasons, including the state of fuel composition. Sealed fuel systems are the future, Tohatsu is now selling a small outboard with fuel injection.

https://www.boats.net/catalog/suzuk...-vin-00601f-510001/carburetor-df6-model-03-04
 

jviss

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Feb 5, 2004
4,627
Tartan 3800 Westport, MA
They just cheaped-out and put interchangeable air jets, on regular, one high-altitude. But, a 2005 engine. I would guess that most carbureted engines of that vintage have air screws.

Carbs may be dying in your view, but in small gas engines I think they will be around forever. It's just so much more complex and expensive to use fuel injection. Carbs are pretty cheap and simple. The only thing that could hasten their demise is draconian emissions regulations. But with Andrew Wheeler that's not happening anytime soon. :)
 
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Adam D

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Sep 8, 2017
12
Catalina 22 Harrison Lake
You guys keep saying to clean the carb but the carb looks incredibly clean. It looked clean before I even cleaned it. Then I cleaned it, with carb cleaner. The jets were easily screwed out and cleaned. I can easily blow air with my mouth through every air and fuel line in the carb. I could before I even cleaned the carb. When I reassembled the carb I left the bowl off for a sec and sprayed carb medic through the orifices to make sure it could pass through. I haven’t tried the ultrasonic business but I’m not convinced it will help.
The external tanks fuel hose, pump, and connectors are not the problem. When I first had the issue I disconnected the external tank and put brand new gas in the internal tank to troubleshoot and make sure it wasn’t a tank issue. The problem exists regardless of what tank I use. I then took the fuel hoses inside the motor off and visually inspected them when I changed the fuel filter. I could see through them clearly and nothing was in them. At this point I am giving up and am going to bring the motor into a shop. Unfortunately that means I will have to wait 3 weeks to get it back but so be it.