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200hp Johnson won't idle

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chawk250

Member
One day, upon returning from fishing trip, I noticed the engine would stall out when I tried to run at slow speed. I changed spark plugs, sprayed carb cleaner and ran it off a remote tank with no noticeable improvement. I does it every time once it comes down from high-idle, it sneezes and stops...any ideas?:mad:
 
One quick and easy thing - check all your fuel lines for air leak. A "sneeze" often indicates an air leak in the fuel system. If you've disconnected the oiling from the VRO/OMS pump, check to make sure the oil line is plugged w/o any air leaks. I had a similar problem with a previous V6 OMC engine I owned and it was caused by the oil inlet of the VR0/OMS pump being capped with a rubber cap which had rotted and was leaking air into the fuel system.
 
Thanks d.b., I looked at fuel lines and they are dry and brittle and in need of replacement anyway. I'll change them tomorrow and let you know. You say it could also be in the oil line from the tank?
 
I am encountering the exact same problem with my 200 Johnson. I have replaced fuel lines, bulb, filters, plugs and cleaned the carbs. I am quite curious to see how to resolve this problem. Still have to try the portable tank though. How did you tie in the portable tank to the engine though? Do you use the fuel line with no adaptor?
 
js, since motor doesn't plug to aux. tank, I stuck the tank end of the fuel line, into the new fuel and pumped the bulb. This seemed to work since engine started, but it continued to stall.
 
chawk250 said:
Thanks d.b., I looked at fuel lines and they are dry and brittle and in need of replacement anyway. I'll change them tomorrow and let you know. You say it could also be in the oil line from the tank?
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I had a sneezing problem at idle, w/ occasional stall on an old V6 engine I had. That engine had a VRO pump with the oil side disconnected. Previous owner had capped the oil inlet on the pump with a rubber cap. It had cracked and was letting a little air in the oil side of the VRO pump. When I replaced the cap, it solved the problem. So yes, based on that experience, air coming into the oil side can cause that problem. Worth trying since it only takes a few minutes to inspect the oil lines and clamps.
 
OK, question here.
Consider an air leak in the fuel line on the input side of the pump, or as d.boat says, in the incoming oil line (or cap). The fuel pump will pull air into the fuel, and pump it through the system, up to the carbs, through the needle and seat, and into the carb bowls. Right?
The carb bowls are vented to the atmosphere. Evidence of that is the flooding over of gas if the needle sticks open.
So, why doesn't the air pulled in by a leak simply rise to the top of the gas in the bowl and rejoin the atmosphere? How can air possibly be sucked through the high speed jet (bottom of bowl)?

Now consider a leak on the output side of the fuel pump. I say there is NO WAY for air to enter the system there, because the fuel in the lines between the pump and carbs is under 3-7 PSI pressure. The only thing that would happen in this example is a fuel leak out of the system.

Anyone?
 
Have you check your idle timing??? you might be just a little off on the timing at idle perhaps idling too low since you come from high speed to low idle and die down you idle might need to be raised a little bit, are you @ ~750 idle RPMs???
 
I don't think it is the fact that the fuel pump will not push the air through the system, it's the fact that the fuel pump will suck air easier than fuel. If you have a very minute air leak on the suction side of the pump, I don't think you would notice it because of your thoughts above. But, if the air leak was large enough, the pump would suck enough air that you would run out of fuel. There is no measurement of how much air it would have to suck before you ran out of fuel.
I didn't see in your post than you have overhauled the carbs, it's 10 years old, maybe time to do it.
 
db>>>finally replaced line, bulb, filter. Seems to run a bit longer before stall @ low idle. Sneezes more like a cough. Sputters a few times, each time rpm's decrease till too slow to run.

js>>>good luck with yours.

nick>>>idle speed 800 rpm on boat tach. I'll try timing then.

dav>>>yeah, carbs are due.

Thank You. ch
 
chawk250 - Did you check compression? As I stated earlier I was having the same problem with my engine and found that I only had 45 psi in my #2 cylinder.
 
Thank you "everyone" for the input. Maybe I'll start a new tread regarding the out come of this. It would seem at this point, that the problem was in the carburators as it has cleared up with the addition of a product called "Sea Foam" into the fuel system at a rate of 16 oz. to 20 gallons. This product came highly recommended for fuel system problems, and "quite possibly" did the trick. It's available everywhere.
 
chawk250 said:
Thank you "everyone" for the input. Maybe I'll start a new tread regarding the out come of this. It would seem at this point, that the problem was in the carburators as it has cleared up with the addition of a product called "Sea Foam" into the fuel system at a rate of 16 oz. to 20 gallons. This product came highly recommended for fuel system problems, and "quite possibly" did the trick. It's available everywhere.
Click to expand...
So did you find the problem?
 
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