My 1999 225 Optimax serial #0G814230 has developed a random misfire in the last two days. The engine began to drop a cylinder or two at idle and would clean up when going to full throttle. When I would slow down the misfire would come back occasionally. I changed the spark plugs NGK 5887 gapped at .033" and it did not help. #2 and #6 plugs had a little more carbon than the rest but I did not think it was too bad as the plugs were fairly old. I plan on changing the fuel filter tomorrow and cutting open the old filter to see if there is any water. Any suggestions on what else to check would be appreciated.