Overheat detection system for outboard motor

A system for detecting overheat of an internal combustion engine for an outboard motor mounted on a boat, whose output is connected to a propeller such that the boat is propelled forward or reverse, comprising:

• a temperature sensor, installed at the engine, which outputs a signal indicative of a temperature of the engine;
• a crank angle sensor, installed at the engine, which outputs a signal indicative of a speed of the engine;
• time measuring means for measuring a period of time since starting of the engine;
• time determining means for determining whether the measured time is within a predetermined first period of time;
• temperature determining means for determining whether the detected engine temperature is equal to or greater than a first predetermined temperature;
• engine speed determining means for determining whether the detected engine speed exceeds a predetermined speed;
• threshold value changing means for changing a threshold value to a value set in a temperature-increasing direction, when the measured time is determined to be within the predetermined first period of time, the detected engine temperature is determined to be equal to or greater than the first predetermined temperature and the detected engine speed is determined to exceed the predetermined speed;
• and
• overheat determining means for comparing the detected engine temperature with the threshold value and for determining that the engine is overheated when the detected engine temperature is determined to exceed the threshold value.