I have a 200 hp 2009 Yamaha 4 stroke and when at idle the overheating alarm sounds after about 12 minutes. I had it to a dealer and they set the idle up to about 900 rpm and the alarm stopped sounding but the manual states that the motor should idle at 700 to 750 there must be something else going on. The motor is new out of the box this year even though it is a 2009. I changed the impeller but to no avail.