I have a 1985 Volvo Penta 225D (305). I was crusing along for around 1/2 hour when I suddenly watched the temp guage steadily rise from where it has sat for years, around 170 degrees when cruising around 3800 RPM, to 240 in less than a minute. The engine began to run very rough and would not accelerate. I immediately brought it to idle and it slowly cooled. <br />After a couple minutes of cooling I was able to run it home at a reasonable temp (180 degrees) at low power settings (1-2000 RPM).<br />I replaced the impeller pump and thermostat. Water appears to flow more freely out of the starboard side exhaust than the port side. I don't know if this is simply caused by being on the hose or some sort of restriction.<br />I have test run it again a couple times since and there is a direct correlation between power settings and temperature and it is still running overall abnormaly hot although it only gets dangerously high at very high RPM's.<br />My inclanation is that I sucked something in that is creating a restriction cooling system. Is there anything else I should look at before tearing into that? If it is a blockage where should I begin? It has dual manifolds and is fresh water cooled.
