2009 yamaha 4 stroke overheating alarm when at idle

[wetbuster]

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.

 

[Silvertip]

Re: 2009 yamaha 4 stroke overheating alarm when at idle

Generally an overheat at idle is due to a thermostat that is stuck closed. You've eliminated the impeller as another possibility. 900 RPM is a bit quick for idle.

 

[schematic]

Re: 2009 yamaha 4 stroke overheating alarm when at idle

wouldn't hurt to check the poppet valve (regulator valve) It might even be missing.....

 

[Silvertip]

Re: 2009 yamaha 4 stroke overheating alarm when at idle

wouldn't hurt to check the poppet valve (regulator valve) It might even be missing.....

The poppet valve opens at higher engine speeds to allow more water flow -- therefore it would not be a factor. If missing or stuck open the engine would over cool, not run hot. If stuck shut the engine would overheat at higher speed. It is designed to be closed at idle to keep engine temp at the proper level. The thermostat is the likely culprit since if it is stuck shut at idle the engine would overheat due to restricted water flow.

 

[schematic]

Re: 2009 yamaha 4 stroke overheating alarm when at idle

A stuck open poppet on some Yamas will prevent the water from even reaching all of the head passages at idle......
Once RPM is raised, volume is increased and all passages are filled.

 

[99yam40]

Re: 2009 yamaha 4 stroke overheating alarm when at idle

I agree.
PRV or PCV which ever way you want to call it, relieves pressure at higher RPMs by dumping water out before going through motor. If stuck open at low RPMs the motor will not fill completely due to dumping the water and you end up with overheat