1990 Supra comp overheat on Deceleration/heat soak?

[Jamesmillerpainting]

Boat info:
1990 Supra comp with pcm ford 351

Symptoms: runs great but after running if you turn ot off to sit for a while when re started it will overheat. If you rev it in neutral it cools off. Also last time out temp would creep up after slowing down. Would run 175 for 45 min straight then when slowing down temp would go up to 185-190. If you stop and rev in neutral it cools off.

Replaced impeller and gaskets I’m early spring. Old impeller was missing fins. Inspected thermostat housing and water pump housing for fins and found one tiny piece.

Was told to check trans cooler. Pulled off trans cooler and there was some debris. One hole was completely clogged. Cleared the blockage. In the process I spilled out a lot of trans oil. I’m wondering now that it’s hooked back up do I need to add more trans fluid? Do I need to flush the trans fluid in case water got in the oil inlet hole when I was flushing the main water passage.

Pulled thermostat housing and it is good. Thinking about trying a 145 instead of a 160 and replacing thermostat.

Noticed a lot of rust near the block where water hoses are behind pulleys (pic included)

I cannot get a mechanic to look at it or I wouldn’t be doing this. Any help is greatly appreciated! Could one clogged hole in the trans cooler really make that much difference


Can’t get pics to upload here’s links to video

https://youtu.be/qjcGeA-84_U

Trans cooler

https://youtu.be/53ScpqhVhR4

[michael hunter]

Check every hose connection on the suction side of the raw water pump. Pull the impeller and inspect for damage [ new doesn't mean good] make sure the thermostat is working it may have been damaged when you installed it upside down. Check the fan belt make sure its tight . If that doesn't fix it check the temp at the thermostat housing to see if the gauge is accurate.

[NoWake]

Good video. My 91 I believe has a 145 degree thermostat and runs around 155. I may use my boat differently than many. Typically free ski on early a.m. glass for a total of around 15 miles (two of us) @ 34-35mph. Could there be a small piece of impeller stuck at the elbow going into your portside exhaust manifold? Be sure to check there. Also look up the exhaust from the transom with a flashlight and verify there are no blockages. You mentioned the port side surges. Some people will find a burnt or defective muffler or other obstruction. One last thought... look for any air leak on the raw water intake and be sure all the hoses before impeller are snug. Hope this helps, good luck
Hopefully someone chimes in on the trans oil.