1990 Johnson Evinrude "ES" 9.9 thru 30 Service Manual, P/N 507871, Page 104Get this manual
Flywheel Servicing
In order to produce the voltage necessary to run an ignition system, the flywheel magnets must be of particular strengthWeak flywheel magnets can cause low ignition voltage which could affect motor performanceWeak flywheel magnets can also cause low readings on ignition test equipment such as the peak-reading voltmeter which may cause unnecessary replacement of ignition componentsFlywheels rarely go bad and would only be replaced as last resort in solving an ignition problem
Removal
1To avoid accidental starting of engine, twist and remove all spark plug leads2Remove the flywheel nut using strap wrench or other suitable tool to hold the flywheel