I have a 60 HP 2 stroke on an 18 ft LOWE. Stars and runs great for about 10 minutes. Up on plane with no problem. After 10-15 mins, It seems as though I lose about half power. It won't plane, and lugs at about 1/4 speed. NOTHING will clear it to resume high speed. tried different tank, different gas, drained carb bowls and on and on. Think there is a coil getting hot? Maybe shutting into safe mode due to heat? Pisser seems to slow when this is happening. No signd of heat, steam, no alarm sounding. Shut it down for a couple hours, starts fine and planes off again and then the same thing in about 10-15 mins. Any thoughts?