"I can't for the life of m
"I can't for the life of me imagine how any change in configuration is going to change the fact that you need to circulate sea(raw)water through something (either the engine itself or a heat exchanger) to remove heat from the engine.
Regardless the type of system (RWC or FWC), there are two circuits and two pumps... one on the engine that circulates water through the engine (just like a car), and one that supplies cool raw water to either the engine itself or the heat exchanger and pushes the hot raw water out of either the engine or the heat exchanger, then out through the risers. You can't just eliminte one of the pumps.
Is the pump completely shot? Typically all you're looking at is an impeller kit... $50."