Cooling system for ford 50

"This is a 1989 Ford 302/5.0 H

"This is a 1989 Ford 302/5.0 HO. This is a buddies boat. He took it to a lake that was very low, got stuck, and started to overheat. He told me the temp got to 220 for a short time, he shut it off at that time. He let it sit for awhile, started it again, this time temp. started to rise again, so he shut it down and took it home. He probably ingested sand,muck and who knows what else. When he got home he ran with the muffs, he said the temp went up to 180 then went down, started to rise again, then he saw smoke come out of the prop exhaust, and the exhaust bellows, shut it off.
Now its up to me to try to fix this problem. I have a good diagram of the upper unit, but cant find the one I need for the engine side. I have one that looks the same, from a 4.3 I think. My question is, is this simaler to the 5.0, or if not where can I get one?
And withe smoke he saw, what should I look for?
Any help would be apprectiated!"

"Maybe this pic will help a bi

"Maybe this pic will help a bit more with flow, the 2 side pics show the t-stat (top is warm and bot is cold), you can pull the input hose off the t-stat and holding it facing up about level with top of engine, start the engine up for a bit (cold engine) and you should have approx 2 to 4 inches of head (drive needs to be in the water not on muffs), this will at least let you know if the problem is before there or after. I would check the impeller and water passages for clogs.

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"Thanks Bob.
This helps alot

"Thanks Bob.
This helps alot. The impeller is the first thing I was going to check, but with this I can go further if need be."