'75 40 hp Johnson will not run at full throttle

twostep

Cadet
Joined
Jun 26, 2002
Messages
10
Motor starts, runs at idle speed pretty good, a little rough. When increased to full throttle the engine will go to full throttle for 5 - 15 minutes then drop back to 50%. From there on it will cycle.<br />Have replaced the fuel pump, carb. kit, points & condenser, plugs and one coil that was loose.<br />Points and plugs were set to manual specs. The motor did the above describe before all the changes.<br />What am I missing? Do I need to check the carb. again? Could it be vacuum problems? Pleas help!
 

fireman 757

Petty Officer 1st Class
Joined
May 18, 2002
Messages
276
Re: '75 40 hp Johnson will not run at full throttle

sounds like an ignition coil goin bad. Pull a plug wire and run it does it do the same thing? Then pull the other. Now what does it do? When you pull one it probably won't start because you are running on one cylinder. Change the bad coil and your in business.
 
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