2005 90 hp alarm question

[1hickory]

First post here so I want to say hello to everyone and thanks for any assistance. As stated, I have a 2005 90 hp 2 stroke. On the last 2 trips out when running wide open, I throttled down when passing through some floating marsh grass. Upon increasing throttle, alarm went off and water peeing seemed excessively hot. After turning off and letting motor sit for approx 15-20 minutes, alarm went off and boat ran fine with no indication of problems the rest of the day. I was thinking it may be the thermostat. Honestly, I'm not excatly sure where the thermostat is, but would like to try and repair myself. I was thinking it was the small rectangular box with aluminum cover near the plugs?
Also, motor has always idled a little high. Is there a simple method of lowering the rpm when idling?
Thanks again for any advice!

[1hickory]

Forgot to mention, a small amount of grass was wrapped around the foot after both times alarm went off, but was easily removed and it didn't appear any debris entered the intake. Good pressure (but almost too hot to touch) peeing also.

[99yam40]

Forgot to mention, a small amount of grass was wrapped around the foot after both times alarm went off, but was easily removed and it didn't appear any debris entered the intake. Good pressure (but almost too hot to touch) peeing also.

If the grass restricted the water intakes then it will cause an over heat.
You should never have to readjust the carbs unless they have been removed and reinstalled. Something must have changed or is going wrong to make it idle too fast.
Can you give more info what RPMs is it running in gear and out?

[jb123]

if it always ran high might just need to adjust idle w/throttle cable

[1hickory]

That's what I was hoping jb. Thanks for the replies. As far as the grass, it never slowed peeing and it seemed like the alarm was more from laying off the throttle from wide open then gunning it again. I was wondering if it had something to do with the thermostat sticking or crap in the thermostat. How difficult is cleaning out the thermostat and I know this shows my lack of knowledge, but where is the thermostat? Thanks again.

[99yam40]

My bet is on the grass restricting water, but if you have never changed the stat or pump it would be a good idea to do that, and check the PRV if it has one. Get a Yamaha service manual if you will be working on this yourself,the one from Yamaha.
Yes it should be at the top of the head, you can look at the parts breakdown of your motor to see where parts are and what they are called while you wait for the manual to get there.
Just click on the Red Purchase Yamaha Parts at the top of the page