Inboard exhaust manifold question

[ggreeby]

All fresh water cooling systems use some sort of heat exchanger ( fresh water to raw water ) . The 1/2 system cools The Engine complete. The full system cools the Engine plus exhaust manifolds , but not the Risers . The risers are raw water cooled that is where the water to keep the rest of the Exhaust system Temp safe, and discharge the Raw water. George