2011 25 hp Mercury 4-stroke (Water pressure issue)

[anderson1775]

So i'm having an issue with my water pressure on the discharge for the cooling system. The discharge will run fine when first put in the water and continue to have great pressure for the first 5 minutes or so. Once i get on plane or put it under a substantial load the water pressure will decrease and become very weak which lead to my overheat sensor kicking off.

I have replaced the thermostat and replaced the water pump. Any ideas will be greatly appreciated

 

[Barnacle_Bill]

Did it just start doing this?

 

[boobie]

Not to be insulting, but did you put the water pump together correctly ?? Sealed correctly and gaskets in place ??