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Johnson keeps stalling at low RPMs

R

rmtworks

Member
Hello,
My 30 hp Johnson is running rough at low idle and then stalls. It's fine in gear at cruising speed. The model # is j30evsia and I bought it around 2001. The fuel filter appears clean. What should I try next?

Thanks,

Chris
 
Carb cleaning if it was sitting for a while. Need more history on motor,, service history,old gas,old fuel tank, Was engine winterized regularly ETC.
 
I would look at my fuel tank and make sure you have no trash or water. Also look to make sure there no build use of old mix oil. Easily identified by black spots lying at bottom of tank. This will with fuel that sets for long time or have had partial fill-ups. Also make sure you use the brand or mix oil consistently.
 
In addition to a carb cleaning, which resolved nothing at the time, my repair involved a blown head gasket replacement along with head resurfacing. Until the issue in the head was fixed it ran like it had carb problems and would die after idling a few minutes at best. I never checked the compression myself but that is how the mechanic said he tracked it down.
 
Do you or did the previous owner use ethanol? Then we can address the fuel system for sure. I repair outboards for a living in the open water months and I can honestly say to you that nearly 50% of my work is because of bad fuel.
 
I would also check the carburetor gaskets that mount to the manifold for air leaks and if it has needles for fuel adjustment at idle check the gaskets around the needle that seal the air off from going around the threads but I have an older motor so I'm not sure about the newer stuff but I figured I would try to at least throw in a helpful word here or there but it sounds like a fuel or carburetor issue with the idling not being good but the top-end being okay sounds like a low in jet is clogged up or varnished
 
Low speed jets.

Fuel-related, it's the carbs 97% of the time. Rebuild the carbs, giving extra attention on the small orifices -- clean them out with a small wire.
 
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