1993 mercury 60 hp beeping problem (really)

[D.D.E.]

my warning beeper on control won't shut off. I was told it could be oil not injecting into motor, but their is oil smoke coming out prop exhaust. The other thing i was told is the beeper sounds when engine is hot, can't be that as it sounds immediately when started. Also a couple times when I turned the key to off, the motor did not shut down. now it does work again. Also the tachometer shows 500 rpm with the key turned (off) and not running, and shows 12 volts on the sender pole of the tac, (gray wire) when i turn the key on, the tachometer jumps to 0 rmp's then does not read any rpm's when motor is running. If anyone could advise me I would greatly appreciate it. I was planning a fishing trip Saturday.
THANKS,DENNIS