continous warning beep

[olefisherman456]

while running motor on muffs thinking of some fall fishing . while running started a continous beep. has plenty of oil, is 95 60 hp mercury on the nitro 160. was very slow to get on plane the last time it was out last spring . was thinking it was old gas and am planning to drain and replace.
i have no owners book and need to know what the beep means . thanks for any info.