Any help would be appreciated... My 2004 Yamaha 225 hpdi Overheat light and buzzer is coming on when I idle around for any extended period of time (waiting to load at boat ramp, looking for structure on graphs, etc.) The pea stream on the motor is working fine, strong constant stream.. If I put the engine in and out of gear about three times while giving the hot foot some gas I can make the buzzer and heat light turn off and the motor runs fine, never have any trouble when I get up and go and make a run.... Any suggestions on what this might be or how to fix it?? Also will it hurt my motor to continue to use the boat as long as I don't idle around long enough that my overheat sensor comes on? thanks

Most likley a stuck or dirty poppet valve Google "HPDI poppet valve"

I would get it fixed before running it again.

Poppet valve and impeller job. Takes about an hour.

I'm having a very similar issue on my Yamaha. I've posted here:

http://texasfishingforum.com/forums/ubbthreads.php/topics/10798239/help_w/_%2704_Yamaha_Vmax_150hp_#Post10798239

I've replaced impeller (the old one was near perfect condition despite being almost 3 years old) and will hopefully change the poppet valve and thermostats this weekend. Work in progress, will report back.

Have you changed the water pump impeller this year? Needs to be changed once a year.

My old Yamaha had same and it was the small elbow in the circulation system was clogged. Did the poppit valve as well. I was fishing in an area with a fine sawdust floating in the water and it clogged the elbow before the P hole.