Hey guys. Got a scare this weekend. Here's a history first that might help. I went to the coast last weekend and put her in Salt water. I did flush it good and hosed the boat down but didn't open the cowling up and stray the inside off. I was fishing ths weekend and drove about 20 minutes to get where I wanted to fish. I didn't stay very,long, maybe 45 minutes but when I cranked the motor, I had a constant BEEEPPPPP going on. i thought it was the oil sensor so I opened up the reserve and added a 1/3 gallon of oil. Welp, it was still going off when I'd turn the key to the on position.
I don't have to crank the motor, just turn the key ON to make the alarm go off. I read today that it's a overheat alarm with a constant beep going on. I had a steady stream of water coming out so it's not the pump. What's ya'll diagnosis? How would you handle the problem.

It's a 2 stroke Merc 125