When i am setting still with my engine(06-175 opti)at idle, the temp climbs. I first knew of this when the
warning sounded(shut down engine right away). If i put engine in gear and run slowly it wants to start to heat up. When i start to run at normal to fast speed(20-60mph) the engine cools down right away and stays cool. Anyone with any ideas of info would br apprec!

Thanks,Terry

Mine did that and I replaced the impellor and it solved the problem, Your impellor is probably worn

I had mine replaced 2 weeks ago while on vacation at Buggs. My motor was doing the exactly the same thing. I cant remember the name of the marine dealer (card is in my truck) that helped me but my vacation would have been a bust without them. They had it back to me in less than 24hours. I know someone on this board knows the name.The shop is located at the west end of the by-pass right next to the new CVS. $125.00 I will be sure to use them when I can. Good luck with yours. One other marine shop wanted 4 or 5 days. If you use them please share this with them and thank them.

I will have to agree with the water pump impeller. Mine had the same symptoms. It was still pumping the water but just not enough.

What is the proper psi at idle and at high end, I have a 03 Mercury 225 EFI and I'm getting around 5-7 psi idle and around 25 psi at high end

On a Merc. you are going into guardian mode is what is happening. You need to replace the impeller without a doubt.your water pressure is ok when running but gets hot while at an idle or under 2000 rpms usually.You probably picked up some sand or trash that damaged it.