Home › Forum › Ask A Member › 1974 Johnson 15 hp runs on 1 cyl at low speed › Re: 1974 Johnson 15 hp runs on 1 cyl at low speed
The 1974 -1976 9.9 and 15 hp have points . The"Fireflash" low tension ignition system can be a bit troublesome,plugs can foul easily. Champ UL81 C gapped @.030 is what the plugs are supposed to be, but i have used NGK B7HS with success. The Champions are hard to find, Marine Engine.com has them.Need the model # for the correct plugs. How long has it been since a complete ignition tune up? If you remove the flywheel you will be able to check the points and test the wiring with an ohmmeter. Timing is critical. As Garry stated,visually inspect the wiring coming out from under the flywheel they flex and move as you move the throttle and the insulation can wear or crack ,causing a short to ground.EDIT
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