it used to. I have tried everything I can think of. My question is "does the raw water pump impeller with 8 blades push less water then one with say 12 or 14?" I replaced the water pump with the spare a year ago and replaced it with a rebuilt one that has a Jabsco impeller with maybe 8 blades. I believe that the original one had many more rubber blades. The engine didn't heat up in Mexico because I put an extra heat exchanger in series with the one installed on the engine. Sense trying to solve the problem permanently I have flushed the engine and replaced the coolant, checked the thermostat and cleaned the heat exchanger. I'm down to replacing the impeller which I don't want to do for the fun of it.