MD2030 Anti-Freeze Leaks

[svcattales]

One of my Volvo MD2030's is blowing antifreeze out the overflow vent at the fill cap. Antifreeze is being replaced by seawater and it is coming through the rubber "ear muff" cap on the forward end of the heat exchanger. I have tightened inner clamp (around round heat exchanger tube) as much as I dare, but seawater is still blowing through. I tried putting a thin layer of RTV silicone around heat exchanger tube before clamping, but no go. I replaced hose clamp with s/s wire via a clamping tool and that held better, but at 2700RPM the leak started again.

This is driving me nuts, because it seems like a simple design, but normal clamps won't keep the ocean out of my heat exchanger and I've wasted lots of anti freeze. Any ideas??