84 Evinrude 90hp misfire

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Yblek3

Cadet
Joined
Mar 12, 2017
Messages
12
My 84 evinrude 90hp misfires on bottom port side cylinder. Carbs have been thoroughly cleaned filter is new plugs are good and firing properly I run it premixed 50:1 and everything seems to be in order but I get a sudden "popapop" when bringing idle down and usually dies. I can't for the life of me figure out why. It starts easy. I've got fuel, air, and ignition. And this engine has been well taken care of. One thing I have noticed is when pulling the plug from the misfired cylinder it has an excessive amount of oil on it. Keep in mind there is no vro and is run premixed. Any suggestions are greatly appreciated! Here is a link to a YouTube video https://youtu.be/jqd-R0Fcgz8
 
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Yblek3

Cadet
Joined
Mar 12, 2017
Messages
12
boobie said:
How have you checked your spark ??
Click to expand...

Spark test was visual. Took the plug out grounded it and watched as the engine turned over. It seems to me that one cylinder is getting too much fuel. This engine has two 2barrel carbs. But I haven't noticed any adjustment screws and I can't find any information about those carburators online.
 
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racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
38,550
Laying plugs on the block is a waste of time !------Does spark jump a gap of 7/16" or more, yes or no ?-------And inspect the diaphragm IF it is running with a regular fuel pump
 
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emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
On these crossflow V-engines, older engines tend to short the bottom spark plugs to the lower cowling latches. Try running it at night and see if there are any spark jumps to ground, with the upper cowling latched in place.
 
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