Spray a little gas in the carbs and try it.If it trys to start you have to rebuild the carbs.If not,spark needss to jump a 1/2" gap.Just holding the plug to the block proves nothing..I am betting a cracked distributor cap under the flywheel.The ignition system is call a low voltage battery cd ignition and you MUST have a very good battery or they will not start and for some reason sears diehard battery do not work.Do not know why just fix enough of theses with a new battery.
Good luck

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23 years marine tech

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