3.0 exhaust manifold over heats

[Ricky_rich]

I have a engine with the cooling system as in the picture.
A new exhaust manifold is installed, new impeller and new thermostat.
The engine it self is not running hot, only exhaust manifold getting to hot. I guess that affects carburetor and intake of gas/air, cause after running full throttle for a minute of two engine dies.
Have tried without thermostat but didn't help. I have a good flow of water from the raw water pump.
Is it possible that there could be something wrong between manifold and elbow that restricts water flow?

 

[Scott Danforth]

Marine engines have constant water flowing to the exhaust manifold.

Verify you have good water flow

 

[Ricky_rich]

Marine engines have constant water flowing to the exhaust manifold.

Verify you have good water flow

Yes that oss what I like to have. But if you look at the picture, there will only be a flow through the manifold when the thermostat is open. The constant flow that come from the bypass in the thermostat house connects after the elbow.
I think its a strange system. Would like to switch the hoses from thermostat house, but the are different sizes. Guess I can solve that part if needed. If I do that modification I get cold water from the impeller pump through manifold all the time, and warm water from open thermostat to go out after the elbow.