hi temp alarm 2001 225 Yamaha

[nativeson]

After running my 2001 225hp Yam in the driveway for about 5 mins, the hi temp alarm goes off. I changed the two thermostats, impeller, and PRV (poppit valve) without any luck. The alarm still goes off after about 3-5 mins idling at 800rpm's (again while the boat is on the trailer in the driveway). I haven't checked the thermoswitches as it seems the odds of those going bad are too low. The tell-tale stream seems at an appropriate rate/force while idling at the low rpm's. Any suggestions or ideas would be greatly appreciated, thanks!

[99yam40]

Monitor temp of heads with gun to see if it is truly overheating, probably plugged up cooling passages

[ptwob212]

Check easy things first. I'd try it in the water, if that's not possible, make sure you have enough water pressure (i.e. a good seal) with the muffs. (you can also run hoses on muffs and the factory flush port at the same time).