My Universal M12 on my 1985 e28+ keeps overheating. I replaced the sea water impeller which was still working fine. Sea water flows freely out the transon exhaust. I replaced the thermostat. I removed the coolant pump which had been replaced by the previous owner. It spins freely and the seals are tight. The impeller on the water pump was slightly rusty but seemed OK. The heat exchanger is cold. Strangley, after the engine overheats, the hot water tank for the sink and shower water system is still cold. That indicates that something is not circulating. The hoses on each side of the water pump are both hot. Any ideas where else to look?
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