My 1986 Mariner 50, 3 cylinder, sounds the temperture alarm (Steady Buzzer)whenever operating the boat at high speed. The alarm goes off as soon as I back off the RPMs to mid range or idle. Good water flow from the telltale at all RPMs. Rebuilt the water pump and tested the temp sensor in boiling water. Open circuit at 212 degrees, closed circuit above 240 degrees. No thermostat on this engine design that I can find. The manual is not clear about thermostat on this engine. What is the next step??
