yamaha low oil/overheating alarm buzzer goes off as soon as I turn key

I have a mid 90s Yamaha 70hp precision blend 2 stroke. I was starting it this morning and as soon as I turned the key the alarm buzzer went off. I have had the outboard for 4 years and this has never happened before. I turned it off and tried it again several times. The oil tank is full. It's not overheating because it was not even started. Any ideas?

 

I do not have the multi function tach. Just the buzzer. An external/temp tach was used to prop the boat by the previous owner.

 

Thanks guys, I found the parts breakdown diagram for the lubrication system. I disconnected the wire coming from the oil level gauge assembly in the remote oil tank. This made the alarm stop. I then drained the oil from the tank. I removed oil level gauge assembly from the tank. The strainer which is at the bottom of the oil level assembly stayed in the tank, I had to fish it out. I reconnected the oil level assembly wire then moved the float up and down. When the float is down it makes contact and the alarm goes off. When the float is raised the alarm does not come on. It seems that it's working properly. I clean everything up and put back together and refilled with fresh yamalube. Turn the key and no alarm. Cranked the boat and it ran as normal for 10 minutes with the lower unit submerged in the test barrel. I took it to the ramp and ran her for about 30 minutes and everything seemed normal. I'm guessing the strainer was holding the float down??? I guess I will keep and eye on it.