Reply To: Weak spark on 1973 20 Hp Johnson

[Don]

OK, so the carb is the exact replacement… From the looks of that powerhead, I’m guessing the carb was toast and you never tried running it with the original carb installed. So, there might be a problem with your replacement carb even though you gave it a basic check/cleaning…. You know what you might try…..Try the carb from your older 20hp on the newer engine, even though all the all the linkages might not hook up perfectly… Once again, are you sure the carb throttle valve is closing fully at idle? You can have a better look at its throttle plate once you remove the carb, perhaps the throttle shaft is binding or something like that. So, now you can’t even get the motor started, is that correct? One or both of the plugs might be fouled from all the sneezing, misfiring. Trying a different carb will give good information quickly. It is safe to “assssume” there is no big problem with your original carb if the engine runs the same way with the older carb installed…Again, please make sure the throttle plate is closing fully at idle…