15 hp Johnson won't start when hot

[bamm_33]

My 15 hp Johnson won't start when hot. Starts first pull after sitting all night long, then after running will not start. I noticed the lower plu is caked with gray carbon. I have replaced coils, rebuilt Carb and replaced fuel pump this year. Any help would be appreciated. thanks in advance

 

[sloopy]

Re: 15 hp Johnson won't start when hot

what is they year?<br />what is the spark plugs you using

 

[bamm_33]

Re: 15 hp Johnson won't start when hot

1983 is the year and the plugs are Champion QL77JC4.

 

[JeremyC_Florida]

Re: 15 hp Johnson won't start when hot

Too much fuel to burn... showing up black around exhaust area? ... timing could be off alittle making it easier to crank while cold (gas is heavy)...after it heats up (gas vapors better)it won't be able to burn fuel.. I'm taking in consideration that your carb is in good working order. You could check your spark on the plugs also... take out " one" plug and run it with plug "out". the 15hp will run alittle higher rpm due to having to compress only the one cylinder. You should see BLUE spark.