if it only does it when you are idling around you likely have a clogged screen, dirty and/or old style poppet valve. An upgrade is available. Could still be a water pump or thermostat, but you need to check your water pressure and look at the tell-tale stream as you go from idle to full throttle. I have had each, the symptoms are all a little different.

I have a 200 hdpi doing the same thing it has a new water pump. What water pressure should it have on plane?

Just recently did impeller kit, both thermostats and poppet valve on mine. Overheat light only came on once idling out of cove but went ahead and did everything at once.

With upgraded Poppet valve, I'm over 20 on plane.

Got a new water pump and impeller in April and last week I noticed my HPDI running about 7-8# WOT. I never got an overheat light and nothing noticeable every seemed wrong on a 4 day lake trip, but I went ahead and dropped it off at the shop on the way home. I am really pissed if they find a problem because it takes 3-4 weeks to get your boat back this time of year. Cant stand leaving my boat at a shop that long.

My Yamaha 200 was doing that and it was the PRV (pressure regulating valve) stuck closed. This valve will open and close regulating the water pressure to the block. Mine was overheating when I was idling around. It was stuck in the closed position which was not allowing water to cool the engine at low RPM. You still need to change the water pump and impeller and if it keeps doing it then replace this. Its located on the top of the motor and easy to change.

Just got a call from shop , cowl was full of dirt dobbers , surprised you did not lose motor , they had R/R lower unit ( insurance ) about 2 weeks prior motor running hot , any one had this happen to them before with dirt dobbers in cowl ?? Motor never ran hot before . But I leave boat in slip . Never thought about cleaning or even checking cowl for obstruction .

Was at Pines, and a guy next to me at the ramp had the same problem. He caught it and had to do the clean out himself (at the ramp).

Those dirt dobbers are great critters, but tough on boats! they also like to fill up your wee-wee hole with mud. You can stick a q-tip in there when you're parked and they'll stay out. I don't know how your cowl is made but maybe you can do something similar.

It's a ox66 ,Yr: 2000 , 200 hp Yammie .

Put a Tough Skinz cover on it. It has mesh that covers the air intake which would keep them out of the cowl.

I would be more worried about the dirt nest breaking apart and sucking into the intake and destroying the motor. I check mine out on a monthly basis. I have my boat in the garage and the little devils still figure out how to get nest built in it.