spark plug fouling on a 2000 50 hp mercury

[Roggie]

Motor has had, minimal use over the last year. Top cylinder keeps fouling plug, compression is 125 or better on each cylinder. spark is good ,getting fuel, but each time I put a new plug in it fouls immediately. Any suggestions ? Thank-you

 

[galamb]

Carb model? Could be running a little rich on the top cylinder. Have the carbs been set since factory?