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1992 Evinrude 120HP, V4 Outboard motor

W

weighs

New member
Project boat/motor: Replaced spark plugs, fuel lines, fuel filters, emptied fuel tank/added ethanol fuel with Sea Foam.
cleaned & added new oil for VRO. Changed water pump. New battery. pulled carbs, cleaned bowl needles. Runs rough,
think a cylinder is not firing! looking for recommendations.
 
In order to fully clean those carbs if it's been sitting a while, you'll need to get carb kits. Bowl needles? I guess you're talking about the float needles. I've attached a link to a diagram for your carbs. You have 3 jets in each carb. Low speed (idle) #13, high speed #14 and intermediate #19. You also need to knock out the plug #2 to get to the small passages under that plug. The carb kit will include a replacement plug. If you've got good compression and a strong spark - as Racerone mentioned, I think you need to give the carbs some needed attention. If the motor is being brought back to live after sitting, the gas has probably evaporated and left behind some sediment that needs to be cleaned out. An air compressor and some forced air through all pasages will be good, but if you don't have access to one the next best thing is a can of carb cleaner with the tiny little straw that attaches to the nozzle.
 
The one cylinder with the compression of 125 does not appear to be firing, (laser heat indication was low compared to the other 3 cylinders after about 5 minutes of operation in the river).
What is practical method to determine if coils are not working?
 
Pull plug wire off with engine idling.-----Motor should slow down and pick up again when you put plug wire back on.----Or you have a plugged carburetor.-----Or issues with crankcase compression ----Or perhaps issues with crankshaft seal rings or reed valves.
 
racerone said:
Pull plug wire off with engine idling.-----Motor should slow down and pick up again when you put plug wire back on.----Or you have a plugged carburetor.-----Or issues with crankcase compression ----Or perhaps issues with crankshaft seal rings or reed valves.
Click to expand...
I will definitely do that. What do you mean by a, “plugged carburetor”? I have seen minor improvement in engine idle operation after using carb spray cleaner over about 2 hours?
 
Ran motor at idle, pulled the plug wire of each of the 4 cylinders, 2 cylinders did nothing, 2 cylinders slowed rpm. Appears there are 2 cylinders not firing. What would be the recommended next step? I plan to check resistance of the coil wires to ensure there isn't an open. Any help would be appreciated. Thanks
 
Post #6 says you have good spark.------Maybe it is not a spark issue.-------Or what color stripe is on the orange wires going to the coils for top cylinders ?
 
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