1986 xp200 with warning horn

[rsemert1]

I have a 1986 xp200 when i turn the key on most but not all the time i get a steady warning horn. It will go off for a couple of minutes of running, then goes off. Most times it will run all day with out reoccurring. Sometime it repeats. Motor runs fine. What could be the cause?

[boats.net]

Steady alarm is overheat warning, Need to check self check alarm module at key switch and temp sensors.

[rsemert1]

How do I go go about making those checks? Thank you for your response.