1990 supra comp overheating

HISTORY:

Got the boat with a bad impellor and a non functioning temp guage.
When I replaced the impeller it was missing fins. I took apart the thermostat housing and there was nothing in there. I found one fin in the water pump housing. Mechanic indicated that if I didn't find anything in either of these locations it had probably blown out the exhaust.

Installed thermostat upside down when I put it back together and overheated (cut off the motor to check it and heard water boiling) but no bad smells or performance issues.

Fixed the temp guage (loose connection)

Took the boat out and it runs right around 175-180 until I stop it. When its not running for a while and I go to start it up it will be over 200 until I run it for a minute and it will cool down. When I hit the throttle it goes down around 150 and slowly starts climbing. Ran the boat through a tank of gas like this (trying not to let it sit and goosing it a little when started to get the water flowing). My "mechanic" was supposed to go through it a month ago and has given me some bum advice in the past. I called him about the temp issue and he suggested a bad water pump housing. Is this kind of behavior normal or will it harm the boat? What should I start doing to make sure that my cooling system is unrestricted and working properly? Where should I check for blockages? If it involves going into the motor thats over my head, but if I can do it by pulling lines and checking around I feel comfortable with that. Boat runs excellent. Steams a very small amount after sitting and then taking off. No funny smells, No performance issues.

Thanks in advance

Normal operating temp is 160 or so . What is the normal running temp? When you shut the engine off the coolant stops flowing and you will get a hot soak until it cools down 200 is not abnormal as long as its cools down once its started. At 175 to 180 its a little hot check all your connections on the suction side of the pump and seals at the strainer and raw water pump .

When its running it generally stays right at 175, but the other day when it was hot out my girlfriend was spinning circles in the thing and it got right around 180-181. So is it safe to say there are probably no impeller pieces buggering up things downstream? Also, what is the strainer and where is it located. I replaced the impeller and all seals associated with the pump about a week ago. Maybe I burned up the impeller when I overheated it, maybe I should check that again. I have a small leak on the exhaust elbows on top on both sides. Ive never seen any water myself but there are stains as if theres a small drip. I replaced the main hose for water intake early this season. Maybe its time to pull all the hoses and replace them.

If your boat has a strainer it will be between the hull water intake and the trans cooler . On the suction side of the raw water pump it is possible to draw in air if any of the hoses or seals are leaking. Check the O ring on the raw water pump. If you can get a Infrared Temperature Gun point it at the thermostat housing it will give you a pretty close reading of the engine temp . It is possible the gauge is off.