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Go Back   SailNet Community > On Board > Gear & Maintenance > Engines > Gas > Atomic 4
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Old 07-24-2013
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Engine almost stalling then recovering

Thought I had cured this problem over the winter,
In the fall, leaving the mooring, the engine would drop rpms
To the point of almost stalling then recover , then repeat ..
It was pulled for the storm before I could do much, but over the winter
I pulled the carb( clean inside, really clean, but I rebuilt it anyway
.) new cap rotor plugs , wires . No water in fuel, changed the fuel filter,
P.o. Installed indigo ignition so no points, installed new coil . When the boat went in I was in a slip for a few weeks , ran it against the łines and it was fine,
Ran it out in fishers island sound a few times probably an hour a time and it aas fine, today leaving the mooring same problem if almost stalling !
Any ideas!? I'm fresh out other than possibly the indigo box is dying..
And the fuel pump moves plenty of fuel( checked it in the fall)..
I'm at wits end ,!crowded mooring with good current , not a good place for problems ... My best solution so far is dumping the boat for something newer!
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Old 07-25-2013
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Re: Engine almost stalling then recovering

Remember the old Texaco commercial: "Do you know what is in your tank?"

Probably not but I have owned a now 45 year old Atomic 4 for over 10 years. Ran into a similar problem that you are experiencing: engine revs unpredictable to the point of stalling.

We had dirty fuel in our tank. We kept cleaning and draining the carburetor but the problem would eventually return. We nearly always found crud in the fuel drained out of the carb by the main passage bolt/plug.

That winter I pumped out our half empty 20 gallon tank and at the bottom of the tank I found what appears in the picture below. This is the result of E10 gasoline that sheds its ethanol which attracts water and breeds bacteria; crud. Your corn tax dollars at work.

Good idea to also replace your rubber fuel lines as they can corrode from the inside and if they are old, they may not be rated for E10 gasoline.

Here is the pic:
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Engine almost stalling then recovering-dirtyfuel.jpg  
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Last edited by CalebD; 07-25-2013 at 12:44 AM.
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Old 07-25-2013
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Re: Engine almost stalling then recovering

My first thought when surging is encountered would be a vacuum leak somewhere. I'm not sure if the Atomic 4 has any vacuum lines or much of a breather system, but check. You could try listening around for leaks with a pipe, one end in your ear.

Other places for a vacuum leak would be inlet manifold gaskets, either manifold to block, or manifold to carb.
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Old 07-25-2013
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Re: Engine almost stalling then recovering

Clogged fuel line vent?
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Re: Engine almost stalling then recovering

Thought about the vent line yesterday,
Ran it with the fuel fill cap off, no difference
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Old 11-09-2013
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Re: Engine almost stalling then recovering

It could be the carb float angle. Often when rebuilding a simple carb such as this, the float bracket is inadvertently bent. This can lead to starving, because the fuel level in the bowl is too low. Here's a youtube vid showing it. The carb is from an outboard, but the function is the same.
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Old 11-09-2013
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Re: Engine almost stalling then recovering

Fuel, spark, air. Most responses think fuel, but you said the carb was clean. Do you have an inline fuel filter between pump and carb? If so, replace it. Can you put a fuel line bulb pump (like on an outboard) after the main fuel filter, before the pump? If you can, then can you keep it from stalling by pumping the bulb? This is now I discovered my fuel pump was weak and stalling intermittently. If it is not the carb, filter or pump you need to go tank diving, or pumping. Get a totally clean tank with fresh gas and then you can rule out fuel. Next spark.
Good luck,
John
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