Does anyone understand how the oil injection system works on a 1987
Mercury?

Is the oil reservoir manually refilled periodically or is it an overflow
from the oil pump?
I had an alarm going off today. When I raised the float, the alarm shut
off. I topped off the oil reservoir and the alarm remained silent.

I found the line from the reservoir to the mixer cracked. Replaced it
and all is well.

Now I need to know is the reservoir there in case the oil injection
fails or as a standby for the external oil tank?

How do I know the oil injection system is working?

Inquiring minds want to know.

John