B
Bob Robeson
We have a 1986 Catalina with the stock Universal M25, 21 HP engine. The temperature is very RPM dependent. The faster I run the engine the hotter its temperature.At 1800 RPM it will run at 165 degrees al daylong.At 2000 RPM it climbs to about 180 degrees but will stay there at day.At 2100 RPM it climbs to 190 plus.Anything above 2100 and the temp just keeps climbing. I do not know how high as at 200 degrees, I have gone to an idle or even shut the engine off.At 2500 RPM it takes less than an hour to go above 200 degrees.Things I have done.1) Replace the fresh water pump and all hoses and the coolant.2) Replaced the raw water pump (impeller)3) Replaced the raw water strainer4) Cleaned the heat exchanger.5) Changed the oil and filter.None of these things have effected the temperature.Things I have been told to try:1) Replace the radiator cap.2) Replace the Thermostat3) Replace the heat exchanger. Ours is bout 2” in diameter.Any ideas of what I should try next.ThanksBobC-36#586