My 2014 Yamaha 250 SHO started making a knocking noise the other day. We thought it could have been bad gas because it had been sitting in the tank for a while and didn't have that pungnet gas smell. Drained the tank and took it out on the water to test it and it was still knocking. We took it to our mechanic and they ran the motor and they said the low oil pressure alarm started going off. They checked the oil levels and everything seemed fine there. They looked at the ecu recorder and it said that the motors low oil pressure alarm had gone off 30 times since we have gotten the motor. I have not heard the alarm go off at all since I have owned the boat.

What could be making my motor knock?

Why haven't I heard the low oil pressure alarm?