Mercury 30hp 4 stroke outboard that keeps overheating?

Question

The engine has been checked by 2 mechanics and they have found that the water flow is correct amount. The heads have been pulled off and checked out to be ok. No gaskets blown

Answer 1

sounds like the carbs are leaning out... too much air to fuel ratio will cause the engine to run hotter.. to much of a "lean" mixture and it will burn holes in the pistons... I suggest checking all the air / fuel passages ,a bigger jet in the carb may be what you need

Answer 2

as it is a four stroke i would say to cheak the timing and richen up your air fuel mixture . because the combustion is way to hot in the cylinder and no it will NOT melt holes in your piston it will shatter the piston or melt it completly or burn up the valves  then you got bigger problems  ........are you sure you just aint running the h**l out of the motor cause that can do it to

Answer 3

check the heads again and have the deck and heads checked to see if any and how much of the surface has been shaved down. it could be possible that someone thought that resurfacing the block and or head would help it power wise and took to much off of one or the other.that would cause the quinch between the head and piston to be too close and generate excessive heat very quickly .