i have a 6hp chrysler outboard that runs awesome and pumps water fine i can troll all day at an idle and run up to about half throttle... anything past half throttle the thing overheats it is pumping water just fine and does not get hot till you plane it out i had my buddy follow me in his boat and while on a plane the water inlet is under water so who can tell me why it only gets hot on a plane i got a 10ft flat bottom jon