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84 mercury 50 hp spark

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Qbanredneck

Contributing Member
2-stroke 1984 mercury 50 hp, did compression check shows 120 on all four cyl. Engine idles and starts fine. New plugs, I noticed top three had oil on them while the bottom one didn’t. of course motor was running neutral to warm engine up for compression test. Thing is I get a feeling the boat is not giving all its got in the water. Just curios as to what else can be? Don’t know last time carbs were cleaned but have done decarb. I know previous owner had boat sitting for a while. Thanks
 
If the bottom plug is totally different from the others there may be an issue with reed valves , no spark or lower crankshaft seals.----Does spark jump a gap of 3/8" ( 1 cm )on all 4 leads , yes or no ?----Could also be an exhaust path blocked with carbon.
 
Thanks, racerone them being surface gap plugs I was unaware a test can be done but if so I can always buy a tester. Though plugs are new can wires not give spark necessary? I’ve looked up the exhaust pipe with LU off and didn’t see blockage, is there anywhere else I can look just in case?
 
The test for strong spark has nothing to do with what plugs are in the engine.-----The plug does not " make the voltage " -----If there is no voltage burst coming to the plug there will be no spark.----Test for spark with a test device , and if there is no spark on one lead then trouble shooting needs to be done.
 
Have completed spark test and all four sparked to 1 cm. I attached a picture just in case I’m looking to much into it. Any help appreciated thanks
 
And if anyone does chime in, the motor starts just fine, and sounds like I would think it should on idle, no sputters or anything.
 
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