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1974 mercury 110 spark issues

M

melonhed

New member
I acquired this motor recently that had been sitting for about 20 years. motor runs briefly at times before cutting out. Seems like a spark issue. When I put a timing light on the wires I get intermittent spark. I remove the plug from the block and ground it, I get consistent spark. Any suggestions?
 
There is a proper test for spark.-----Does spark jump a gap of 3/8" consistently on a test device , yes or no ?-------Sounds like you need to look at the fuel pump and carburetor.----And you need to install a new water pump impeller on it.
 
no it does not consistently jump a 3/8" gap when I got it it also had the wrong spark plugs. already redid the carburetor so it is getting fuel. It won't fire at all with the correct plugs. inspected the coils, and both have a minor crack in the orange plastic on the backside.
 
Might be, or bad wires, or a bad coil (seen lots of those).

If the wires look okay (rotted insulation is common) I'd try swapping the coils and see if the problem shifts to the other cylinder. (You may need to do a plug test first, to see which cylinder is sagging on you.)

By the way, forcing the spark to jump a much wider gap will also (usually) indicate which plug is not getting enough spark.


Jeff

PS: Those are really good running motors, so hang in there.
 
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