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1985 Mercury 25 XD - No Spark

J

Johnr314

New member
I defer to those who have probably forgotten more about outboards than I will ever know so here it goes. I have a 1985 Mercury 25 XD which was running this time last year. I did have to put a new water pump on it and figured that was all that was needed however, it fails to start. I have pulled the plugs and cannot get spark to the plug. I disconnected the black/yellow wire leading to the tiller engine stop button and still no spark. I am running out of stuff to try for my feeble understanding. Any ideas????
 
are you making sure you grounding the plug to engine when testing. It will not spark if you just pull plug and put plug wire on it. Hold plug against engine ground while turning engine over and look for spark.
 
Most definitely. Held it to ground myself, and then had someone else hold it to ground. I don't have a compression gauge but the compression on both cylinders seems to be low to me. Have no problem holding a thumb over the plug hole while turning it over. Some neighbors borrowed the boat last year and I think they were not watching and the power head overheated. They did tell me they thought the the water pump needed to be fixed when they brought it back. Guess that is what we get for loaning it out..... At any rate, the tiller engine stop button is the only kill button I can find this particular motor.
 
Do the compression test before anything else is DONE!! To do a correct spark test you need an open air spark tester. If the motor overheated you may have much bigger problems.
 
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OK guys, so, after buying a compression test gauge and an open spark test kit. Here are the results:
Compression on both cylinders is right at 90 so I think I am good there. I did notice that the head bolts were not torqued so I torqued them back down to specifications given. The open air spark still indicated nothing. I removed the flywheel to inspect the stator assembly which "looked" pretty good. I began going through every wire I could possibly find and noticed (3) three wires coming from the control box to the double coil set which were melted through just enough to barely see wire on the under side of the wire. After all I have done and looked at, I thought I found the issue however, after repairing these wires, I still have no spark and considering what I know about outboards (nothing), I believe I am down to the stator and/or the coils. Tell me what you guys think and let me know if there is a way to test the stator and the coils but please keep the verbiage simple. If weighed and measured on outboard mechanical knowledge, I would be found wanting.

Much thanks to all
 
7 years later... just curious, have you found the problem, i am at the same place.
replaced the coils, and the wire. Tested to see if there is a short and have enough juce, but still no fire.
 
7 years later... just curious, have you found the problem, i am at the same place.
replaced the coils, and the wire. Tested to see if there is a short and have enough juce, but still no fire.
:(
 
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